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Updated: Thursday, March 14, 2019
 
 

rksh (1)

Name

rksh - gramming language

Synopsis

ksh [ +-abcefhikmnoprstuvxBCDP ] [ -R file ] [ +-o option ] ... [ - ] [
arg ... ]
rksh  [ +-abcefhikmnoprstuvxBCD ] [ -R file ] [ +-o option ] ...  [ - ]
[ arg ... ]

Description

KSH(1)                      General Commands Manual                     KSH(1)



NAME
       ksh,  rksh,  pfksh  - KornShell, a standard/restricted command and pro-
       gramming language

SYNOPSIS
       ksh [ +-abcefhikmnoprstuvxBCDP ] [ -R file ] [ +-o option ] ... [ - ] [
       arg ... ]
       rksh  [ +-abcefhikmnoprstuvxBCD ] [ -R file ] [ +-o option ] ...  [ - ]
       [ arg ... ]

DESCRIPTION
       Ksh is a command and programming language that executes  commands  read
       from a terminal or a file.  Rksh is a restricted version of the command
       interpreter ksh; it is used to set up login names and  execution  envi-
       ronments whose capabilities are more controlled than those of the stan-
       dard shell.  Rpfksh is a profile shell version of  the  command  inter-
       preter ksh; it is used to to execute commands with the attributes spec-
       ified by the user's profiles (see pfexec(1)).  See Invocation below for
       the meaning of arguments to the shell.

   Definitions.
       A metacharacter is one of the following characters:

              ;   &   (   )   |   <   >   new-line   space   tab

       A  blank  is a tab or a space.  An identifier is a sequence of letters,
       digits, or underscores starting with a letter or  underscore.   Identi-
       fiers  are used as components of variable names.  A vname is a sequence
       of one or more identifiers separated by a . and optionally preceded  by
       a  ..   Vnames  are  used  as function and variable names.  A word is a
       sequence of characters from the character set defined  by  the  current
       locale, excluding non-quoted metacharacters.

       A  command  is a sequence of characters in the syntax of the shell lan-
       guage.  The shell reads each command and carries out the desired action
       either  directly or by invoking separate utilities.  A built-in command
       is a command that is carried out by the shell itself without creating a
       separate  process.   Some  commands are built-in purely for convenience
       and are not documented here.  Built-ins that cause side effects in  the
       shell environment and built-ins that are found before performing a path
       search (see Execution below) are documented here.  For historical  rea-
       sons,  some  of these built-ins behave differently than other built-ins
       and are called special built-ins.

   Commands.
       A simple-command is  a  list  of  variable  assignments  (see  Variable
       Assignments  below) or a sequence of blank separated words which may be
       preceded by a list of variable  assignments  (see  Environment  below).
       The  first  word  specifies  the  name  of  the command to be executed.
       Except as specified below, the remaining words are passed as  arguments
       to  the invoked command.  The command name is passed as argument 0 (see
       exec(2)).  The value of a simple-command is its exit status;  0-255  if
       it  terminates  normally;  256+signum  if it terminates abnormally (the
       name of the signal corresponding to the exit status can be obtained via
       the -l option of the kill built-in utility).

       A  pipeline  is a sequence of one or more commands separated by |.  The
       standard output of each command but the last is connected by a  pipe(2)
       to the standard input of the next command.  Each command, except possi-
       bly the last, is run as a separate process; the  shell  waits  for  the
       last  command  to terminate.  The exit status of a pipeline is the exit
       status of the last command unless the pipefail option is enabled.  Each
       pipeline  can be preceded by the reserved word !  which causes the exit
       status of the pipeline to become 0 if the exit status of the last  com-
       mand is non-zero, and 1 if the exit status of the last command is 0.

       A  list  is  a sequence of one or more pipelines separated by ;, &, |&,
       &&, or ||, and optionally terminated by ;, &, or  |&.   Of  these  five
       symbols,  ;,  &, and |& have equal precedence, which is lower than that
       of && and ||.  The symbols && and || also  have  equal  precedence.   A
       semicolon (;) causes sequential execution of the preceding pipeline; an
       ampersand (&) causes asynchronous execution of the  preceding  pipeline
       (i.e.,  the shell does not wait for that pipeline to finish).  The sym-
       bol |& causes asynchronous execution of the preceding pipeline  with  a
       two-way  pipe  established  to the parent shell; the standard input and
       output of the spawned pipeline can be written to and read from  by  the
       parent shell by applying the redirection operators <& and >& with arg p
       to commands and by using -p option of the built-in  commands  read  and
       print described later.  The symbol && (||) causes the list following it
       to be executed only if the preceding pipeline returns a zero (non-zero)
       value.   One  or more new-lines may appear in a list instead of a semi-
       colon, to delimit a command.  The first item  of the first pipeline  of
       a  list  that is a simple command not beginning with a redirection, and
       not occurring within a while, until, or if list, can be preceded  by  a
       semicolon.   This  semicolon  is  ignored  unless  the showme option is
       enabled as described with the set built-in below.

       A command is either a simple-command or one of the  following.   Unless
       otherwise  stated,  the value returned by a command is that of the last
       simple-command executed in the command.

       for vname [ in word ... ] ;do list ;done
              Each time a for command is executed, vname is set  to  the  next
              word  taken  from the in word list.  If in word ...  is omitted,
              then the for command executes the do list once  for  each  posi-
              tional  parameter  that  is  set  starting from 1 (see Parameter
              Expansion below).  Execution ends when there are no  more  words
              in the list.

       for (( [expr1] ; [expr2] ; [expr3] )) ;do list ;done
              The  arithmetic  expression expr1 is evaluated first (see Arith-
              metic evaluation below).  The  arithmetic  expression  expr2  is
              repeatedly  evaluated  until  it evaluates to zero and when non-
              zero, list is executed and the arithmetic expression expr3 eval-
              uated.   If  any expression is omitted, then it behaves as if it
              evaluated to 1.

       select vname [ in word ... ] ;do list ;done
              A select command prints on standard error  (file  descriptor  2)
              the set of words, each preceded by a number.  If in word ...  is
              omitted, then the positional parameters starting from 1 are used
              instead  (see  Parameter  Expansion  below).   The PS3 prompt is
              printed and a line is read from the  standard  input.   If  this
              line consists of the number of one of the listed words, then the
              value of the variable vname is set to the word corresponding  to
              this  number.   If  this  line  is  empty, the selection list is
              printed again.  Otherwise the value of the variable vname is set
              to  null.   The contents of the line read from standard input is
              saved in the variable REPLY.  The  list  is  executed  for  each
              selection  until  a break or end-of-file is encountered.  If the
              REPLY variable is set to null by the execution of list, then the
              selection  list  is printed before displaying the PS3 prompt for
              the next selection.

       case word in [ [(]pattern [ | pattern ] ... ) list ;; ] ... esac
              A case command executes the list associated with the first  pat-
              tern that matches word.  The form of the patterns is the same as
              that used for file-name generation  (see  File  Name  Generation
              below).   The ;; operator causes execution of case to terminate.
              If ;& is used in place of ;; the next subsequent list,  if  any,
              is executed.

       if list ;then list [ ;elif list ;then list ] ... [ ;else list ] ;fi
              The list following if is executed and, if it returns a zero exit
              status, the list following the first then is  executed.   Other-
              wise,  the  list following elif is executed and, if its value is
              zero, the list following the next  then  is  executed.   Failing
              each successive elif list, the else list is executed.  If the if
              list has non-zero exit status and there is no  else  list,  then
              the if command returns a zero exit status.

       while list ;do list ;done
       until list ;do list ;done
              A  while  command repeatedly executes the while list and, if the
              exit status of the last command in the list  is  zero,  executes
              the  do  list; otherwise the loop terminates.  If no commands in
              the do list are executed, then the while command returns a  zero
              exit  status;  until may be used in place of while to negate the
              loop termination test.

       ((expression))
              The expression is evaluated using the rules for arithmetic eval-
              uation  described below.  If the value of the arithmetic expres-
              sion is non-zero, the exit status is 0, otherwise the exit  sta-
              tus is 1.

       (list)
              Execute list in a separate environment.  Note, that if two adja-
              cent open parentheses are needed for nesting, a  space  must  be
              inserted  to  avoid  evaluation  as  an  arithmetic  command  as
              described above.

       { list;}
              list is simply executed.  Note that unlike the metacharacters  (
              and  ),  { and } are reserved words and must occur at the begin-
              ning of a line or after a ; in order to be recognized.

       [[ expression ]]
              Evaluates expression and returns a zero exit status when expres-
              sion is true.  See Conditional Expressions below, for a descrip-
              tion of expression.

       function varname { list ;}
       varname () { list ;}
              Define a function which is referenced by  varname.   A  function
              whose  varname contains a .  is called a discipline function and
              the portion of the varname preceding the last .  must  refer  to
              an  existing  variable.  The body of the function is the list of
              commands between { and }.  A function defined with the  function
              varname syntax can also be used as an argument to the .  special
              built-in command to get the equivalent behavior as if  the  var-
              name() syntax were used to define it.  (See Functions below.)

       namespace identifier { list ;}
              Defines  or uses the name space identifier and runs the commands
              in list in this name space.  (See Name Spaces below.)

       & [ name [ arg... ]  ]
              Causes subsequent list commands terminated by & to be placed  in
              the  background  job  pool  name.   If name is omitted a default
              unnamed pool is used.  Commands in a named background  pool  may
              be executed remotely.

       time [ pipeline ]
              If  pipeline is omitted the user and system time for the current
              shell and completed  child  processes  is  printed  on  standard
              error.   Otherwise, pipeline is executed and the elapsed time as
              well as the user and system time are printed on standard  error.
              The TIMEFORMAT variable may be set to a format string that spec-
              ifies how the timing information should be displayed.  See Shell
              Variables below for a description of the TIMEFORMAT variable.

       The  following reserved words are recognized as reserved only when they
       are the first word of a command and are not quoted:

       if then else elif fi case esac for while until do  done  {  }  function
       select time [[ ]] !

   Variable Assignments.
       One  or  more variable assignments can start a simple command or can be
       arguments to the typeset, enum, export, or  readonly  special  built-in
       commands  as  well  as  to other declaration commands created as types.
       The syntax for an assignment is of the form:

       varname=word
       varname[word]=word
              No space is permitted between varname and the = or between = and
              word.

       varname=(assign_list)
              No  space  is permitted between varname and the =.  The variable
              varname is unset before the assignment.  An assign_list  can  be
              one of the following:
                      word ...
                             Indexed array assignment.
                      [word]=word ...
                             Associative  array  assignment.   If  preceded by
                             typeset -a this  will  create  an  indexed  array
                             instead.
                      assignment ...
                             Compound  variable  assignment.   This  creates a
                             compound variable varname with  sub-variables  of
                             the  form  varname.name,  where  name is the name
                             portion of assignment.  The value of varname will
                             contain  all the assignment elements.  Additional
                             assignments made to sub-variables of varname will
                             also  be  displayed  as part of the value of var-
                             name.  If no assignments are  specified,  varname
                             will  be a compound variable allowing subsequence
                             child elements to be defined.
                      typeset [options] assignment ...
                             Nested variable assignment.  Multiple assignments
                             can  be specified by separating each of them with
                             a ;.  The previous  value  is  unset  before  the
                             assignment.   Other  declaration commands such as
                             readonly, enum, and  other  declaration  commands
                             can be used in place of typeset.
                      . filename
                             Include  the  assignment  commands  contained  in
                             filename.

       In addition, a += can be used in place of the = to signify adding to or
       appending  to  the previous value.  When += is applied to an arithmetic
       type, word is evaluated as an arithmetic expression and  added  to  the
       current value.  When applied to a string variable, the value defined by
       word is appended to the value.  For compound assignments, the  previous
       value  is not unset and the new values are appended to the current ones
       provided that the types are compatible.

       The right hand side of a variable assignment undergoes all  the  expan-
       sion listed below except word splitting, brace expansion, and file name
       generation.  When the left hand side is an  assignment  is  a  compound
       variable  and  the  right  hand is the name of a compound variable, the
       compound variable on the right will be copied or appended to  the  com-
       pound variable on the left.

   Comments.
       A  word beginning with # causes that word and all the following charac-
       ters up to a new-line to be ignored.
   Aliasing.
       The first word of each command is replaced by the text of an  alias  if
       an alias for this word has been defined.  An alias name consists of any
       number of characters excluding metacharacters, quoting characters, file
       expansion  characters,  parameter  expansion  and  command substitution
       characters, the characters / and =.  The replacement string can contain
       any  valid shell script including the metacharacters listed above.  The
       first word of each command in the replaced text, other  than  any  that
       are  in  the process of being replaced, will be tested for aliases.  If
       the last character of the alias value is a blank then the word  follow-
       ing the alias will also be checked for alias substitution.  Aliases can
       be used to redefine built-in commands but cannot be  used  to  redefine
       the  reserved  words  listed  above.  Aliases can be created and listed
       with the alias command and can be removed with the unalias command.
       Aliasing is performed when scripts are read, not while  they  are  exe-
       cuted.   Therefore,  for  an alias to take effect, the alias definition
       command has to be executed before  the  command  which  references  the
       alias is read.
       The  following  aliases are compiled into the shell but can be unset or
       redefined:
                           autoload='typeset -fu'
                           command='command  '
                           compound='typeset -C'
                           fc=hist
                           float='typeset -lE'
                           functions='typeset -f'
                           hash='alias -t --'
                           history='hist -l'
                           integer='typeset -li'
                           nameref='typeset -n'
                           nohup='nohup  '
                           r='hist -s'
                           redirect='command exec'
                           source='command .'
                           stop='kill -s STOP'
                           suspend='kill -s STOP $$'
                           times='{ { time;} 2>&1;}'
                           type='whence -v'

   Tilde Substitution.
       After alias substitution is performed, each word is checked to  see  if
       it begins with an unquoted ~.  For tilde substitution, word also refers
       to the word portion of parameter  expansion  (see  Parameter  Expansion
       below).   If  it  does, then the word up to a / is checked to see if it
       matches a user name in the password database (See getpwname(3).)  If  a
       match  is  found,  the ~ and the matched login name are replaced by the
       login directory of the matched user.  If no match is found, the  origi-
       nal  text  is  left  unchanged.   A ~ by itself, or in front of a /, is
       replaced by $HOME.  A ~ followed by a + or - is replaced by  the  value
       of $PWD and $OLDPWD respectively.

       In  addition,  when expanding a variable assignment, tilde substitution
       is attempted when the value of the assignment begins with a ~, and when
       a ~ appears after a :.  The : also terminates a ~ login name.

   Command Substitution.
       The  standard  output  from a command list enclosed in parentheses pre-
       ceded by a dollar sign ( $(list) ), or in a brace group preceded  by  a
       dollar  sign  (  ${ list;} ), or in a pair of grave accents (``) may be
       used as part or all of a word; trailing new-lines are removed.  In  the
       second case, the { and } are treated as a reserved words so that { must
       be followed by a blank and } must appear at the beginning of  the  line
       or  follow  a  ;.  In the third (obsolete) form, the string between the
       quotes is processed for special quoting characters before  the  command
       is  executed (see Quoting below).  The command substitution $(cat file)
       can be replaced by the equivalent but  faster  $(<file).   The  command
       substitution  $(n<#)  will  expand  to the current byte offset for file
       descriptor n.  Except for the second form, the command list is run in a
       subshell  so  that  no side effects are possible.  For the second form,
       the final } will be recognized as a reserved word after any token.

   Arithmetic Substitution.
       An arithmetic expression enclosed in double parentheses preceded  by  a
       dollar  sign  (  $(())  )  is  replaced  by the value of the arithmetic
       expression within the double parentheses.

   Process Substitution.
       Each command argument of the form <(list) or >(list) will  run  process
       list asynchronously connected to some file in /dev/fd if this directory
       exists, or else a fifo a temporary directory.  The name  of  this  file
       will  become  the  argument  to  the  command.   If  the form with > is
       selected then writing on this file will provide input for list.   If  <
       is used, then the file passed as an argument will contain the output of
       the list process.  For example,

              paste <(cut -f1  file1)  <(cut  -f3  file2)  |  tee  >(process1)
              >(process2)

       cuts fields 1 and 3 from the files file1 and file2 respectively, pastes
       the results together, and  sends  it  to  the  processes  process1  and
       process2,  as  well  as putting it onto the standard output.  Note that
       the file, which is passed as an argument to  the  command,  is  a  UNIX
       pipe(2) so programs that expect to lseek(2) on the file will not work.

       Process  substitution  of  the form <(list) can also be used with the <
       redirection operator which causes the output of  list  to  be  standard
       input or the input for whatever file descriptor is specified.

   Parameter Expansion.
       A parameter is a variable, one or more digits, or any of the characters
       *, @, #, ?, -, $, and !.  A variable is denoted by a vname.  To  create
       a variable whose vname contains a ., a variable whose vname consists of
       everything before the last . must already  exist.   A  variable  has  a
       value  and  zero  or more attributes.  Variables can be assigned values
       and attributes by using the  typeset  special  built-in  command.   The
       attributes  supported by the shell are described later with the typeset
       special  built-in  command.   Exported  variables   pass   values   and
       attributes to the environment.

       The  shell supports both indexed and associative arrays.  An element of
       an array variable is referenced by a subscript.   A  subscript  for  an
       indexed  array  is  denoted by an arithmetic expression (see Arithmetic
       evaluation below) between a [ and a ].  To assign values to an  indexed
       array, use vname=(value ...) or set -A vname  value ... .  The value of
       all  non-negative  subscripts  must  be  in  the  range  of  0  through
       4,194,303.  A negative subscript is treated as an offset from the maxi-
       mum current index +1 so that -1 refers to the  last  element.   Indexed
       arrays  can  be declared with the -a option to typeset.  Indexed arrays
       need not be declared.  Any reference to a variable with  a  valid  sub-
       script is legal and an array will be created if necessary.

       An  associative array is created with the -A option to typeset.  A sub-
       script for an associative array is denoted by a string enclosed between
       [ and ].

       Referencing  any array without a subscript is equivalent to referencing
       the array with subscript 0.

       The value of a variable may be assigned by writing:

              vname=value [ vname=value ] ...

       or
              vname[subscript]=value [ vname[subscript]=value ] ...
       Note that no space is allowed before or after the =.
       Attributes assigned by the typeset special built-in  command  apply  to
       all  elements of the array.  An array element can be a simple variable,
       a compound variable or an array variable.  An  element  of  an  indexed
       array  can be either an indexed array or an associative array.  An ele-
       ment of an associative array can also be either.  To refer to an  array
       element  that is part of an array element, concatenate the subscript in
       brackets.  For example, to refer to the foobar element of  an  associa-
       tive  array  that is defined as the third element of the indexed array,
       use ${vname[3][foobar]}
       A nameref is a variable that is a reference  to  another  variable.   A
       nameref  is created with the -n attribute of typeset.  The value of the
       variable at the time of the typeset command becomes the  variable  that
       will  be referenced whenever the nameref variable is used.  The name of
       a nameref cannot contain a ..  When a variable or  function  name  con-
       tains  a  .,  and the portion of the name up to the first . matches the
       name of a nameref, the variable referred to is  obtained  by  replacing
       the  nameref  portion  with  the name of the variable referenced by the
       nameref.  If a nameref is used as the index of a for loop, a name  ref-
       erence  is established for each item in the list.  A nameref provides a
       convenient way to refer to the variable inside a function whose name is
       passed  as  an  argument  to a function.  For example, if the name of a
       variable is passed as the first argument to a function, the command
              typeset -n var=$1
       inside the function causes references and assignments to var to be ref-
       erences  and  assignments to the variable whose name has been passed to
       the function.
       If any of the floating point attributes, -E, -F, or -X, or the  integer
       attribute,  -i,  is  set for vname, then the value is subject to arith-
       metic evaluation as described below.
       Positional parameters, parameters denoted by a number, may be  assigned
       values with the set special built-in command.  Parameter $0 is set from
       argument zero when the shell is invoked.
       The character $ is used to introduce substitutable parameters.
       ${parameter}
              The shell reads all the characters from ${ to the matching }  as
              part  of the same word even if it contains braces or metacharac-
              ters.  The value, if any, of the parameter is substituted.   The
              braces  are  required  when  parameter  is followed by a letter,
              digit, or underscore that is not to be interpreted  as  part  of
              its  name,  when the variable name contains a ..  The braces are
              also required when a variable is subscripted unless it  is  part
              of  an  Arithmetic  Expression  or a Conditional Expression.  If
              parameter is one or more digits then it is a positional  parame-
              ter.   A  positional  parameter  of  more than one digit must be
              enclosed in braces.  If parameter is * or @, then all the  posi-
              tional  parameters, starting with $1, are substituted (separated
              by a field separator character).  If an array  vname  with  last
              subscript  *  @,  or for index arrays of the form sub1 ..  sub2.
              is used, then the value for each of the  elements  between  sub1
              and sub2 inclusive (or all elements for * and @) is substituted,
              separated by the first character of the value of IFS.
       ${#parameter}
              If parameter is * or @, the number of positional  parameters  is
              substituted.   Otherwise, the length of the value of the parame-
              ter is substituted.
       ${#vname[*]}
       ${#vname[@]}
              The number of elements in the array vname is substituted.

       ${@vname}
              Expands to  the  type  name  (See  Type  Variables    below)  or
              attributes of the variable referred to by vname.
       ${!vname}
              Expands  to the name of the variable referred to by vname.  This
              will be vname except when vname is a name reference.
       ${!vname[subscript]}
              Expands to name of the subscript unless subscript is *,  @.   or
              of  the  form  sub1  ..  sub2.  When subscript is *, the list of
              array subscripts for vname is generated.  For a variable that is
              not  an array, the value is 0 if the variable is set.  Otherwise
              it is null.  When subscript is @, same  as  above,  except  that
              when  used in double quotes, each array subscript yields a sepa-
              rate argument.  When subscript is of the form sub1 ..   sub2  it
              expands  to  the list of subscripts between sub1 and sub2 inclu-
              sive using the same quoting rules as @.
       ${!prefix*}
              Expands to the names of the variables  whose  names  begin  with
              prefix.
       ${parameter:-word}
              If  parameter  is set and is non-null then substitute its value;
              otherwise substitute word.
       ${parameter:=word}
              If parameter is not set or is null then  set  it  to  word;  the
              value  of the parameter is then substituted.  Positional parame-
              ters may not be assigned to in this way.
       ${parameter:?word}
              If parameter is set and is non-null then substitute  its  value;
              otherwise,  print  word and exit from the shell (if not interac-
              tive).  If word is omitted then a standard message is printed.
       ${parameter:+word}
              If parameter is set and is non-null then substitute word; other-
              wise substitute nothing.
       In the above, word is not evaluated unless it is to be used as the sub-
       stituted string, so that, in the following  example,  pwd  is  executed
       only if d is not set or is null:
              print ${d:-$(pwd)}
       If  the  colon  (  :  ) is omitted from the above expressions, then the
       shell only checks whether parameter is set or not.
       ${parameter:offset:length}
       ${parameter:offset}
              Expands to the portion of the value of parameter starting at the
              character (counting from 0) determined by expanding offset as an
              arithmetic expression and consisting of the number of characters
              determined  by  the arithmetic expression defined by length.  In
              the second form, the remainder of the value is used.  If A nega-
              tive  offset  counts  backwards from the end of parameter.  Note
              that one or more blanks is required in front of a minus sign  to
              prevent  the  shell  from  interpreting  the operator as :-.  If
              parameter is * or @, or is an array name indexed by * or @, then
              offset  and  length  refer to the array index and number of ele-
              ments respectively.  A negative offset is taken relative to  one
              greater  than  the  highest  subscript  for indexed arrays.  The
              order for associate arrays is unspecified.
       ${parameter#pattern}
       ${parameter##pattern}
              If the shell pattern matches  the  beginning  of  the  value  of
              parameter,  then the value of this expansion is the value of the
              parameter with the matched portion deleted; otherwise the  value
              of  this parameter is substituted.  In the first form the small-
              est matching pattern is deleted  and  in  the  second  form  the
              largest matching pattern is deleted.  When parameter is @, *, or
              an array variable with subscript @ or *, the substring operation
              is applied to each element in turn.

       ${parameter%pattern}
       ${parameter%%pattern}
              If  the shell pattern matches the end of the value of parameter,
              then the value of this expansion is the value of  the  parameter
              with the matched part deleted; otherwise substitute the value of
              parameter.  In the first form the smallest matching  pattern  is
              deleted  and  in the second form the largest matching pattern is
              deleted.  When parameter is @, *, or an array variable with sub-
              script  @  or *, the substring operation is applied to each ele-
              ment in turn.

       ${parameter/pattern/string}
       ${parameter//pattern/string}
       ${parameter/#pattern/string}
       ${parameter/%pattern/string}
              Expands parameter and replaces the longest match of pattern with
              the  given  string.  Each occurrence of \n in string is replaced
              by the portion of parameter that matches the  n-th  sub-pattern.
              In  the  first  form,  only  the  first occurrence of pattern is
              replaced.  In  the  second  form,  each  match  for  pattern  is
              replaced by the given string.  The third form restricts the pat-
              tern match to the beginning of the string while the fourth  form
              restricts  the  pattern  match  to  the end of the string.  When
              string is null, the pattern will be deleted and the /  in  front
              of  string  may be omitted.  When parameter is @, *, or an array
              variable with subscript @ or *, the  substitution  operation  is
              applied  to each element in turn.  In this case, the string por-
              tion of word will be re-evaluated for each element.

       The following parameters are automatically set by the shell:
              #      The number of positional parameters in decimal.
              -      Options supplied to the shell on invocation or by the set
                     command.
              ?      The decimal value returned by the last executed command.
              $      The process number of this shell.
              _      Initially,  the value of _ is an absolute pathname of the
                     shell or script being executed as passed in the  environ-
                     ment.   Subsequently  it is assigned the last argument of
                     the previous command.  This parameter is not set for com-
                     mands  which  are  asynchronous.   This parameter is also
                     used to hold the name of  the  matching  MAIL  file  when
                     checking for mail.  While defining a compound variable or
                     a type, _ is initialized as a reference to  the  compound
                     variable or type.  When a discipline function is invoked,
                     _ is initialized as a reference to the  variable  associ-
                     ated  with  the call to this function.  Finally when _ is
                     used as the name of the first variable of a type  defini-
                     tion,  the new type is derived from the type of the first
                     variable (See Type Variables  below.).
              !      The process id or the pool name and  job  number  of  the
                     last  background  command  invoked or the most recent job
                     put in the  background  with  the  bg  built-in  command.
                     Background  jobs  started  in a named pool will be in the
                     form pool.number where pool is the pool name  and  number
                     is the job number within that pool.
              .sh.command
                     When  processing a DEBUG trap, this variable contains the
                     current command line that is about to run.
              .sh.edchar
                     This variable contains the value of the keyboard  charac-
                     ter  (or sequence of characters if the first character is
                     an ESC, ascii 033) that has been entered when  processing
                     a  KEYBD  trap (see Key Bindings below).  If the value is
                     changed as part of the trap action, then  the  new  value
                     replaces the key (or key sequence) that caused the trap.
              .sh.edcol
                     The  character  position of the cursor at the time of the
                     most recent KEYBD trap.
              .sh.edmode
                     The value is set to ESC  when  processing  a  KEYBD  trap
                     while  in  vi insert mode.  (See Vi Editing Mode  below.)
                     Otherwise, .sh.edmode is null  when  processing  a  KEYBD
                     trap.
              .sh.edtext
                     The  characters  in  the  input buffer at the time of the
                     most recent KEYBD trap.  The value is null when not  pro-
                     cessing a KEYBD trap.
              .sh.file
                     The  pathname  of the file than contains the current com-
                     mand.
              .sh.fun
                     The name of the current function that is being executed.
              .sh.level
                     Set to the current function depth.  This can  be  changed
                     inside a DEBUG trap and will set the context to the spec-
                     ified level.
              .sh.lineno
                     Set during a DEBUG trap to the line number for the caller
                     of each function.
              .sh.match
                     An  indexed  array which stores the most recent match and
                     sub-pattern matches  after  conditional  pattern  matches
                     that match and after variables expansions using the oper-
                     ators #, %, or /.  The 0-th element stores  the  complete
                     match  and  the  i-th.  element stores the i-th submatch.
                     The .sh.match variable becomes unset  when  the  variable
                     that has expanded is assigned a new value.
              .sh.math
                     Used  for  defining  arithmetic functions (see Arithmetic
                     evaluation below).  and stores the list of  user  defined
                     arithmetic functions.
              .sh.name
                     Set to the name of the variable at the time that a disci-
                     pline function is invoked.
              .sh.subscript
                     Set to the name subscript of the  variable  at  the  time
                     that a discipline function is invoked.
              .sh.subshell
                     The current depth for subshells and command substitution.
              .sh.value
                     Set to the value of the variable at the time that the set
                     or append discipline function is invoked.   When  a  user
                     defined  arithmetic  function  is  invoked,  the value of
                     .sh.value is saved and .sh.value is set  to  long  double
                     precision floating point.  .sh.value is restored when the
                     function returns.
              .sh.version
                     Set to a value that identifies the version of this shell.
              KSH_VERSION
                     A name reference to .sh.version.
              LINENO The current line number within  the  script  or  function
                     being executed.
              OLDPWD The previous working directory set by the cd command.
              OPTARG The  value  of  the last option argument processed by the
                     getopts built-in command.
              OPTIND The index of the last option argument  processed  by  the
                     getopts built-in command.
              PPID   The process number of the parent of the shell.
              PWD    The present working directory set by the cd command.
              RANDOM Each  time this variable is referenced, a random integer,
                     uniformly distributed between 0 and 32767, is  generated.
                     The  sequence  of  random  numbers  can be initialized by
                     assigning a numeric value to RANDOM.
              REPLY  This variable is set by the select statement and  by  the
                     read built-in command when no arguments are supplied.
              SECONDS
                     Each time this variable is referenced, the number of sec-
                     onds since shell invocation is returned.  If  this  vari-
                     able  is  assigned  a value, then the value returned upon
                     reference will be the value that was  assigned  plus  the
                     number of seconds since the assignment.
              SHLVL  An  integer  variable  the  is  incremented each time the
                     shell is invoked and is exported.  If SHLVL is not in the
                     environment when the shell is invoked, it is set to 1.

       The following variables are used by the shell:
              CDPATH The search path for the cd command.
              COLUMNS
                     If  this variable is set, the value is used to define the
                     width of the edit window for the shell edit modes and for
                     printing select lists.
              EDITOR If  the  VISUAL  variable  is  not set, the value of this
                     variable will be checked for the  patterns  as  described
                     with  VISUAL  below  and the corresponding editing option
                     (see Special Command set below) will be turned on.
              ENV    If this variable is set, then parameter  expansion,  com-
                     mand  substitution,  and arithmetic substitution are per-
                     formed on the value  to  generate  the  pathname  of  the
                     script  that  will  be executed when the shell is invoked
                     interactively (see Invocation below).  This file is typi-
                     cally  used  for  alias  and  function  definitions.  The
                     default value is $HOME/.kshrc.  On systems that support a
                     system  wide   /etc/ksh.kshrc initialization file, if the
                     filename generated by the expansion of  ENV  begins  with
                     /./  or ././ the system wide initialization file will not
                     be executed.
              FCEDIT Obsolete name for the default editor name  for  the  hist
                     command.  FCEDIT is not used when HISTEDIT is set.
              FIGNORE
                     A  pattern that defines the set of filenames that will be
                     ignored when performing filename matching.
              FPATH  The search path for function definitions.   The  directo-
                     ries  in  this path are searched for a file with the same
                     name as the function or command when a function with  the
                     -u  attribute  is  referenced  and  when a command is not
                     found.  If an executable file with the name of that  com-
                     mand  is  found, then it is read and executed in the cur-
                     rent environment.  Unlike  PATH,  the  current  directory
                     must be represented explicitly by .  rather than by adja-
                     cent : characters or a beginning or ending :.
              HISTCMD
                     Number of the current command in the history file.
              HISTEDIT
                     Name for the default editor name for the hist command.
              HISTFILE
                     If this variable is set when the shell is  invoked,  then
                     the  value  is the pathname of the file that will be used
                     to  store  the  command  history  (see  Command  Re-entry
                     below).
              HISTSIZE
                     If  this  variable is set when the shell is invoked, then
                     the number of previously entered commands that are acces-
                     sible by this shell will be greater than or equal to this
                     number.  The default is 512.
              HOME   The default argument (home directory) for the cd command.
              IFS    Internal field separators, normally space, tab, and  new-
                     line  that  are  used  to separate the results of command
                     substitution  or  parameter  expansion  and  to  separate
                     fields with the built-in command read.  The first charac-
                     ter of the IFS variable is used to separate arguments for
                     the  "$*"  substitution (see Quoting below).  Each single
                     occurrence of an IFS character in the string to be split,
                     that is not in the isspace character class, and any adja-
                     cent characters in IFS that are in the isspace  character
                     class,  delimit  a  field.  One or more characters in IFS
                     that belong to the isspace  character  class,  delimit  a
                     field.   In  addition,  if  the  same  isspace  character
                     appears  consecutively  inside  IFS,  this  character  is
                     treated  as  if it were not in the isspace class, so that
                     if IFS consists of two tab characters, then two  adjacent
                     tab characters delimit a null field.
              JOBMAX This  variable  defines  the maximum number running back-
                     ground jobs that can run at a time.  When this  limit  is
                     reached, the shell will wait for a job to complete before
                     staring a new job.
              LANG   This variable determines the locale category for any cat-
                     egory  not specifically selected with a variable starting
                     with LC_ or LANG.
              LC_ALL This variable overrides the value of  the  LANG  variable
                     and any other LC_ variable.
              LC_COLLATE
                     This  variable determines the locale category for charac-
                     ter collation information.
              LC_CTYPE
                     This variable determines the locale category for  charac-
                     ter  handling  functions.   It  determines  the character
                     classes for pattern matching (see  File  Name  Generation
                     below).
              LC_NUMERIC
                     This variable determines the locale category for the dec-
                     imal point character.
              LINES  If this variable is set, the value is used  to  determine
                     the  column  length  for  printing  select lists.  Select
                     lists will print vertically  until  about  two-thirds  of
                     LINES lines are filled.
              MAIL   If  this  variable  is set to the name of a mail file and
                     the MAILPATH variable is not set, then the shell  informs
                     the user of arrival of mail in the specified file.
              MAILCHECK
                     This  variable specifies how often (in seconds) the shell
                     will check for changes in the modification time of any of
                     the  files  specified  by the MAILPATH or MAIL variables.
                     The default value is 600  seconds.   When  the  time  has
                     elapsed  the  shell  will  check  before issuing the next
                     prompt.
              MAILPATH
                     A colon ( : ) separated list  of  file  names.   If  this
                     variable  is  set, then the shell informs the user of any
                     modifications to the specified files that  have  occurred
                     within the last MAILCHECK seconds.  Each file name can be
                     followed by a ?  and a message that will be printed.  The
                     message will undergo parameter expansion, command substi-
                     tution, and arithmetic substitution with the variable  $_
                     defined  as  the  name of the file that has changed.  The
                     default message is you have mail in $_.
              PATH   The search path for commands (see Execution below).   The
                     user  may not change PATH if executing under rksh (except
                     in .profile).
              PS1    The value of this  variable  is  expanded  for  parameter
                     expansion, command substitution, and arithmetic substitu-
                     tion to define the primary prompt string which by default
                     is  ``$''.  The character !  in the primary prompt string
                     is replaced by the command number (see  Command  Re-entry
                     below).   Two successive occurrences of !  will produce a
                     single !  when the prompt string is printed.
              PS2    Secondary prompt string, by default ``> ''.
              PS3    Selection prompt string used within  a  select  loop,  by
                     default ``#? ''.
              PS4    The  value  of  this  variable  is expanded for parameter
                     evaluation, command substitution, and arithmetic  substi-
                     tution  and precedes each line of an execution trace.  By
                     default, PS4 is ``+ ''.  In addition when PS4  is  unset,
                     the execution trace prompt is also ``+ ''.
              SHELL  The pathname of the shell is kept in the environment.  At
                     invocation, if the basename  of  this  variable  is  rsh,
                     rksh,  or krsh, then the shell becomes restricted.  If it
                     is pfsh or pfksh, then the shell becomes a profile  shell
                     (see pfexec(1)).
              TIMEFORMAT
                     The  value  of  this parameter is used as a format string
                     specifying how the timing information for pipelines  pre-
                     fixed  with  the  time reserved word should be displayed.
                     The % character introduces  a  format  sequence  that  is
                     expanded  to a time value or other information.  The for-
                     mat sequences and their meanings are as follows.
                     %%        A literal %.
                     %[p][l]R  The elapsed time in seconds.
                     %[p][l]U  The number of CPU seconds spent in user mode.
                     %[p][l]S  The number of CPU seconds spent in system mode.
                     %P        The CPU percentage, computed as (U + S) / R.

                     The brackets denote optional portions.  The optional p is
                     a  digit  specifying  the  precision, the number of frac-
                     tional digits after a decimal point.  A value of 0 causes
                     no decimal point or fraction to be output.  At most three
                     places after the decimal point can be  displayed;  values
                     of p greater than 3 are treated as 3.  If p is not speci-
                     fied, the value 3 is used.

                     The optional l specifies a longer format, including hours
                     if  greater  than  zero, minutes, and seconds of the form
                     HHhMMmSS.FFs.  The value of p determines whether  or  not
                     the fraction is included.

                     All  other  characters  are  output  without change and a
                     trailing newline is added.  If unset, the default  value,
                     $'\nreal\t%2lR\nuser\t%2lU\nsys%2lS',  is  used.   If the
                     value is null, no timing information is displayed.

              TMOUT  If set to a value greater than zero, TMOUT  will  be  the
                     default timeout value for the read built-in command.  The
                     select compound command terminates  after  TMOUT  seconds
                     when input is from a terminal.  Otherwise, the shell will
                     terminate if a line is not entered within the  prescribed
                     number  of  seconds while reading from a terminal.  (Note
                     that the shell can be compiled with a maximum  bound  for
                     this value which cannot be exceeded.)

              VISUAL If  the  value  of  this  variable  matches  the  pattern
                     *[Vv][Ii]*, then the vi option (see Special  Command  set
                     below)  is  turned  on.  If the value matches the pattern
                     *gmacs* , the gmacs option is turned on.   If  the  value
                     matches the pattern *macs*, then the emacs option will be
                     turned on.  The value of VISUAL overrides  the  value  of
                     EDITOR.

       The  shell gives default values to PATH, PS1, PS2, PS3, PS4, MAILCHECK,
       FCEDIT, TMOUT and IFS, while HOME, SHELL, ENV, and MAIL are not set  at
       all  by  the shell (although HOME is set by login(1)).  On some systems
       MAIL and SHELL are also set by login(1).

   Field Splitting.
       After parameter expansion and command substitution, the results of sub-
       stitutions  are scanned for the field separator characters (those found
       in IFS) and split into distinct fields where such characters are found.
       Explicit  null  fields  (""  or '') are retained.  Implicit null fields
       (those resulting from parameters that have no values or command substi-
       tutions with no output) are removed.

       If the braceexpand (-B) option is set then each of the fields resulting
       from IFS are checked to see if they contain one or more  of  the  brace
       patterns  {*,*},  {l1..l2} , {n1..n2} , {n1..n2% fmt} , {n1..n2 ..n3} ,
       or {n1..n2 ..n3%fmt} , where * represents any character, l1,l2 are let-
       ters  and  n1,n2,n3 are signed numbers and fmt is a format specified as
       used by printf.  In each case, fields are  created  by  prepending  the
       characters  before  the  {  and appending the characters after the } to
       each of the strings generated by the characters between the  {  and  }.
       The  resulting  fields  are  checked to see if they have any brace pat-
       terns.

       In the first form, a field is created for each string between { and  ,,
       between  , and ,, and between , and }.  The string represented by * can
       contain embedded matching { and } without quoting.  Otherwise,  each  {
       and } with * must be quoted.

       In  the  seconds form, l1 and l2 must both be either upper case or both
       be lower case characters in the C locale.  In this case a field is cre-
       ated for each character from l1 thru l2.

       In  the remaining forms, a field is created for each number starting at
       n1 and continuing until it reaches n2 incrementing n1 by n3.  The cases
       where n3 is not specified behave as if n3 where 1 if n1<=n2 and -1 oth-
       erwise.  If forms which specify %fmt any format flags, widths and  pre-
       cisions  can  be  specified  and  fmt  can end in any of the specifiers
       cdiouxX.  For  example,  {a,z}{1..5..3%02d}{b..c}x  expands  to  the  8
       fields, a01bx, a01cx, a04bx, a04cx, z01bx, z01cx, z04bx and z4cx.

   File Name Generation.
       Following  splitting, each field is scanned for the characters *, ?, (,
       and [ unless the -f option has been set.  If one  of  these  characters
       appears, then the word is regarded as a pattern.  Each file name compo-
       nent that contains any pattern character is  replaced  with  a  lexico-
       graphically  sorted  set  of  names  that matches the pattern from that
       directory.  If no file name is found that  matches  the  pattern,  then
       that  component of the filename is left unchanged unless the pattern is
       prefixed with ~(N) in which case it is removed as described below.   If
       FIGNORE  is set, then each file name component that matches the pattern
       defined by the value of FIGNORE is ignored when generating the matching
       filenames.   The  names .  and ..  are also ignored.  If FIGNORE is not
       set, the character .  at the start of each file name component will  be
       ignored unless the first character of the pattern corresponding to this
       component is the character .  itself.  Note, that  for  other  uses  of
       pattern matching the / and .  are not treated specially.

              *      Matches any string, including the null string.  When used
                     for filename expansion, if the globstar option is on, two
                     adjacent  *'s  by itself will match all files and zero or
                     more directories and subdirectories.  If followed by a  /
                     then only directories and subdirectories will match.
              ?      Matches any single character.
              [...]  Matches  any  one  of the enclosed characters.  A pair of
                     characters separated by - matches any character lexically
                     between the pair, inclusive.  If the first character fol-
                     lowing the opening [ is a !  or ^ then any character  not
                     enclosed  is matched.  A - can be included in the charac-
                     ter set by putting it as the first or last character.
                     Within [ and ], character classes can be  specified  with
                     the  syntax [:class:] where class is one of the following
                     classes defined in the ANSI-C standard: (Note  that  word
                     is equivalent to alnum plus the character _.)
                     alnum  alpha  blank  cntrl  digit graph lower print punct
                     space upper word xdigit
                     Within [ and ], an equivalence  class  can  be  specified
                     with  the  syntax [=c=] which matches all characters with
                     the same primary collation weight (as defined by the cur-
                     rent  locale) as the character c.  Within [ and ], [.sym-
                     bol.]  matches the collating symbol symbol.
       A pattern-list is a list of one or more patterns  separated  from  each
       other  with  a & or |.  A & signifies that all patterns must be matched
       whereas | requires that only one pattern be  matched.   Composite  pat-
       terns can be formed with one or more of the following sub-patterns:
              ?(pattern-list)
                     Optionally matches any one of the given patterns.
              *(pattern-list)
                     Matches zero or more occurrences of the given patterns.
              +(pattern-list)
                     Matches one or more occurrences of the given patterns.
              {n}(pattern-list)
                     Matches n occurrences of the given patterns.
              {m,n}(pattern-list)
                     Matches  from  m  to n occurrences of the given patterns.
                     If m is omitted, 0 will be used.   If  n  is  omitted  at
                     least m occurrences will be matched.
              @(pattern-list)
                     Matches exactly one of the given patterns.
              !(pattern-list)
                     Matches anything except one of the given patterns.
       By  default, each pattern, or sub-pattern will match the longest string
       possible consistent with generating the longest overall match.  If more
       than  one  match is possible, the one starting closest to the beginning
       of the string will be chosen.   However, for each of the above compound
       patterns  a  -  can be inserted in front of the ( to cause the shortest
       match to the specified pattern-list to be used.

       When pattern-list is contained within parentheses, the backslash  char-
       acter  \ is treated specially even when inside a character class.   All
       ANSI-C character escapes are recognized and match the specified charac-
       ter.  In addition the following escape sequences are recognized:
              \d     Matches any character in the digit class.
              \D     Matches any character not in the digit class.
              \s     Matches any character in the space class.
              \S     Matches any character not in the space class.
              \w     Matches any character in the word class.
              \W     Matches any character not in the word class.

       A  pattern  of the form %(pattern-pair(s)) is a sub-pattern that can be
       used to match nested character expressions.  Each pattern-pair is a two
       character sequence which cannot contain & or |.  The first pattern-pair
       specifies the starting and ending characters for the match.  Each  sub-
       sequent  pattern-pair represents the beginning and ending characters of
       a nested group that will be skipped over  when  counting  starting  and
       ending  character  matches.  The behavior is unspecified when the first
       character of a pattern-pair is alpha-numeric except for the following:
              D      Causes the ending character to terminate the  search  for
                     this pattern without finding a match.
              E      Causes  the  ending  character  to  be  interpreted as an
                     escape character.
              L      Causes the ending character to be interpreted as a  quote
                     character causing all characters to be ignored when look-
                     ing for a match.
              Q      Causes the ending character to be interpreted as a  quote
                     character  causing  all  characters other than any escape
                     character to be ignored when looking for a match.
       Thus, %({}Q"E\), matches characters starting at { until the matching  }
       is  found not counting any { or } that is inside a double quoted string
       or preceded by the escape character \.  Without  the  {}  this  pattern
       matches any C language string.

       Each  sub-pattern in a composite pattern is numbered, starting at 1, by
       the location of the ( within the pattern.  The sequence \n, where n  is
       a  single  digit  and \n comes after the n-th. sub-pattern, matches the
       same string as the sub-pattern itself.

       Finally a pattern can contain sub-patterns of the  form  ~(options:pat-
       tern-list),  where  either  options  or  :pattern-list  can be omitted.
       Unlike the other compound patterns, these sub-patterns are not  counted
       in  the  numbered  sub-patterns.   :pattern-list  must  be  omitted for
       options F, G, N , and V below.  If options is present, it  can  consist
       of one or more of the following:
              +      Enable the following options.  This is the default.
              -      Disable the following options.
              E      The  remainder  of  the  pattern  uses  extended  regular
                     expression syntax like the egrep(1) command.
              F      The remainder of the  pattern  uses  fgrep(1)  expression
                     syntax.
              G      The  remainder  of the pattern uses basic regular expres-
                     sion syntax like the grep(1) command.
              K      The remainder of the pattern uses shell  pattern  syntax.
                     This is the default.
              N      This  is  ignored.   However, when it is the first letter
                     and is used with file name  generation,  and  no  matches
                     occur, the file pattern expands to the empty string.
              X      The  remainder  of  the  pattern  uses  augmented regular
                     expression syntax like the xgrep(1) command.
              P      The remainder of the pattern uses perl(1) regular expres-
                     sion  syntax.   Not all perl regular expression syntax is
                     currently implemented.
              V      The remainder  of  the  pattern  uses  System  V  regular
                     expression syntax.
              i      Treat the match as case insensitive.
              g      File the longest match (greedy).  This is the default.
              l      Left anchor the pattern.  This is the default for K style
                     patterns.
              r      Right anchor the pattern.  This  is  the  default  for  K
                     style patterns.
       If both options and :pattern-list are specified, then the options apply
       only to  pattern-list.  Otherwise, these options remain in effect until
       they  are disabled by a subsequent ~(...) or at the end of the sub-pat-
       tern containing ~(...).

   Quoting.
       Each of the metacharacters listed earlier (see Definitions above) has a
       special  meaning  to  the shell and causes termination of a word unless
       quoted.  A character may be quoted (i.e., made to stand for itself)  by
       preceding  it with a \.  The pair \new-line is removed.  All characters
       enclosed between a pair of single quote marks ('') that is not preceded
       by  a  $  are  quoted.   A single quote cannot appear within the single
       quotes.  A single quoted string preceded by an unquoted $ is  processed
       as an ANSI-C string except for the following:
       \0     Causes the remainder of the string to be ignored.
       \E     Equivalent to the escape character (ascii 033),
       \e     Equivalent to the escape character (ascii 033),
       \cx    Expands to the character control-x.
       \C[.name.]
              Expands to the collating element name.

       Inside  double  quote  marks  (""),  parameter and command substitution
       occur and \ quotes the characters \, `, ", and $.  A $ in  front  of  a
       double  quoted string will be ignored in the "C" or "POSIX" locale, and
       may cause the string to be replaced by a locale specific string  other-
       wise.   The  meaning  of $* and $@ is identical when not quoted or when
       used as a variable assignment value or as a file name.   However,  when
       used  as a command argument, "$*" is equivalent to "$1d$2d...", where d
       is the first character of the IFS variable, whereas "$@" is  equivalent
       to  "$1" "$2" ....  Inside grave quote marks (``), \ quotes the charac-
       ters \, `, and $.  If the grave quotes occur within double quotes, then
       \ also quotes the character ".

       The  special  meaning  of  reserved  words or aliases can be removed by
       quoting any character of the reserved word.  The recognition  of  func-
       tion  names or built-in command names listed below cannot be altered by
       quoting them.

   Arithmetic Evaluation.
       The shell performs arithmetic evaluation for  arithmetic  substitution,
       to  evaluate  an  arithmetic command, to evaluate an indexed array sub-
       script, and to evaluate arguments to the built-in  commands  shift  and
       let.   Evaluations  are performed using double precision floating point
       arithmetic or long double precision floating  point  for  systems  that
       provide  this  data  type.   Floating point constants follow the ANSI-C
       programming language floating point conventions.   The  floating  point
       constants Nan and Inf can be use to represent "not a number" and infin-
       ity respectively.  Integer constants follow the ANSI-C programming lan-
       guage  integer constant conventions although only single byte character
       constants are recognized and character casts are  not  recognized.   In
       addition  constants can be of the form [base#]n where base is a decimal
       number between two and sixty-four representing the arithmetic base  and
       n  is a number in that base.  The digits above 9 are represented by the
       lower case letters, the upper case letters, @, and _ respectively.  For
       bases  less than or equal to 36, upper and lower case characters can be
       used interchangeably.

       An arithmetic expression uses the same syntax, precedence, and associa-
       tivity  of  expression as the C language.  All the C language operators
       that apply to floating point quantities can be used.  In addition,  the
       operator  **  can be used for exponentiation.  It has higher precedence
       than multiplication and is left associative.   In  addition,  when  the
       value of an arithmetic variable or sub-expression can be represented as
       a long integer, all C language integer  arithmetic  operations  can  be
       performed.   Variables  can  be referenced by name within an arithmetic
       expression without using the parameter expansion syntax.  When a  vari-
       able is referenced, its value is evaluated as an arithmetic expression.

       Any  of  the  following  math  library functions that are in the C math
       library can be used within an arithmetic expression:

       abs acos acosh asin asinh atan atan2 atanh cbrt ceil copysign cos  cosh
       erf erfc exp exp2 expm1 fabs fpclassify fdim finite floor fma fmax fmin
       fmod hypot ilogb int isfinite sinf isnan isnormal issubnormal  issubor-
       dered  iszero  j0  j1 jn lgamma log log10 log2 logb nearbyint nextafter
       nexttoward pow remainder rint round scanb signbit  sin  sinh  sqrt  tan
       tanh  tgamma  trunc  y0  y1 yn In addition, arithmetic functions can be
       define as shell functions with a variant of the function name syntax,

       function .sh.math.name ident ... { list ;}
              where name is the function name used in the  arithmetic  expres-
              sion  and each identifier, ident is a name reference to the long
              double  precision  floating  point  argument.   The   value   of
              .sh.value  when  the function returns is the value of this func-
              tion.  User defined functions can take up  to  3  arguments  and
              override C math library functions.

       An internal representation of a variable as a double precision floating
       point can be specified with the -E [n], -F [n], or -X [n] option of the
       typeset  special  built-in command.  The -E option causes the expansion
       of the value to be represented using scientific  notation  when  it  is
       expanded.  The optional option argument n defines the number of signif-
       icant figures.  The -F option causes the expansion to be represented as
       a floating decimal number when it is expanded.  The -X option cause the
       expansion to be represented using the %a format defined  by  ISO  C-99.
       The  optional  option argument n defines the number of places after the
       decimal (or radix) point in this case.

       An internal integer representation of a variable can be specified  with
       the  -i  [n]  option  of  the  typeset  special  built-in command.  The
       optional option argument n specifies an arithmetic base to be used when
       expanding the variable.  If you do not specify an arithmetic base, base
       10 will be used.

       Arithmetic evaluation is performed on the value of each assignment to a
       variable  with  the  -E, -F, -X, or -i attribute.  Assigning a floating
       point number to a variable whose type is an integer  causes  the  frac-
       tional part to be truncated.

   Prompting.
       When  used interactively, the shell prompts with the value of PS1 after
       expanding it for parameter expansion, command substitution, and  arith-
       metic substitution, before reading a command.  In addition, each single
       !  in the prompt is replaced by the command number.  A !!  is  required
       to place !  in the prompt.  If at any time a new-line is typed and fur-
       ther input is needed to complete a command, then the  secondary  prompt
       (i.e., the value of PS2) is issued.

   Conditional Expressions.
       A  conditional  expression is used with the [[ compound command to test
       attributes of files and to compare strings.  Field splitting  and  file
       name generation are not performed on the words between [[ and ]].  Each
       expression can be constructed from one or more of the  following  unary
       or binary expressions:
       string True, if string is not null.
       -a file
              Same as -e below.  This is obsolete.
       -b file
              True, if file exists and is a block special file.
       -c file
              True, if file exists and is a character special file.
       -d file
              True, if file exists and is a directory.
       -e file
              True, if file exists.
       -f file
              True, if file exists and is an ordinary file.
       -g file
              True, if file exists and it has its setgid bit set.
       -k file
              True, if file exists and it has its sticky bit set.
       -n string
              True, if length of string is non-zero.
       -o ?option
              True, if option named option is a valid option name.
       -o option
              True, if option named option is on.
       -p file
              True, if file exists and is a fifo special file or a pipe.
       -r file
              True, if file exists and is readable by current process.
       -s file
              True, if file exists and has size greater than zero.
       -t fildes
              True,  if  file  descriptor number fildes is open and associated
              with a terminal device.
       -u file
              True, if file exists and it has its setuid bit set.
       -v name
              True, if variable name is a valid variable name and is set.
       -w file
              True, if file exists and is writable by current process.
       -x file
              True, if file exists and is executable by current  process.   If
              file exists and is a directory, then true if the current process
              has permission to search in the directory.
       -z string
              True, if length of string is zero.
       -L file
              True, if file exists and is a symbolic link.
       -h file
              True, if file exists and is a symbolic link.
       -N file
              True, if file exists and the modification time is  greater  than
              the last access time.
       -O file
              True,  if  file  exists and is owned by the effective user id of
              this process.
       -G file
              True, if file exists and its group matches the  effective  group
              id of this process.
       -R name
              True if variable name is a name reference.
       -S file
              True, if file exists and is a socket.
       file1 -nt file2
              True, if file1 exists and file2 does not, or file1 is newer than
              file2.
       file1 -ot file2
              True, if file2 exists and file1 does not, or file1 is older than
              file2.
       file1 -ef file2
              True, if file1 and file2 exist and refer to the same file.
       string == pattern
              True,  if  string  matches  pattern.  Any part of pattern can be
              quoted to cause it to be matched as a string.  With a successful
              match  to  a  pattern, the .sh.match array variable will contain
              the match and sub-pattern matches.
       string = pattern
              Same as == above, but is obsolete.
       string != pattern
              True, if string does not match pattern.  When the string matches
              the  pattern the .sh.match array variable will contain the match
              and sub-pattern matches.
       string =~ ere
              True if string matches the  pattern  ~(E)ere  where  ere  is  an
              extended regular expression.
       string1 < string2
              True,  if  string1  comes before string2 based on ASCII value of
              their characters.
       string1 > string2
              True, if string1 comes after string2 based  on  ASCII  value  of
              their characters.
       The following obsolete arithmetic comparisons are also permitted:
       exp1 -eq exp2
              True, if exp1 is equal to exp2.
       exp1 -ne exp2
              True, if exp1 is not equal to exp2.
       exp1 -lt exp2
              True, if exp1 is less than exp2.
       exp1 -gt exp2
              True, if exp1 is greater than exp2.
       exp1 -le exp2
              True, if exp1 is less than or equal to exp2.
       exp1 -ge exp2
              True, if exp1 is greater than or equal to exp2.

       In  each  of  the  above expressions, if file is of the form /dev/fd/n,
       where n is an integer, then the test is applied to the open file  whose
       descriptor number is n.

       A compound expression can be constructed from these primitives by using
       any of the following, listed in decreasing order of precedence.
       (expression)
              True, if expression is true.  Used to group expressions.
       ! expression
              True if expression is false.
       expression1 && expression2
              True, if expression1 and expression2 are both true.
       expression1 || expression2
              True, if either expression1 or expression2 is true.

   Input/Output.
       Before a command is executed, its input and output  may  be  redirected
       using  a  special notation interpreted by the shell.  The following may
       appear anywhere in a simple-command or may precede or follow a  command
       and  are  not  passed on to the invoked command.  Command substitution,
       parameter expansion, and arithmetic substitution occur before  word  or
       digit  is used except as noted below.  File name generation occurs only
       if the shell is interactive and the  pattern  matches  a  single  file.
       Field splitting is not performed.

       In  each  of  the  following  redirections,  if  file  is  of  the form
       /dev/sctp/host/port, /dev/tcp/host/port, or  /dev/udp/host/port,  where
       host is a hostname or host address, and port is a service given by name
       or an integer port number, then the redirection attempts to make a tcp,
       sctp or udp connection to the corresponding socket.

       No  intervening  space is allowed between the characters of redirection
       operators.

       <word         Use file word as standard input (file descriptor 0).

       >word         Use file word as standard output (file descriptor 1).  If
                     the  file does not exist then it is created.  If the file
                     exists, and the noclobber option is on,  this  causes  an
                     error; otherwise, it is truncated to zero length.

       >|word        Same as >, except that it overrides the noclobber option.

       >;word        Write  output  to  a temporary file.  If the command com-
                     pletes successfully rename it to word, otherwise,  delete
                     the  temporary  file.   >;word  cannot  be  used with the
                     exec(2).  built-in.

       >>word        Use file word as standard output.  If  the  file  exists,
                     then  output  is  appended to it (by first seeking to the
                     end-of-file); otherwise, the file is created.

       <>word        Open file word for reading and writing as  standard  out-
                     put.

       <>;word       The  same  as <>word except that if the command completes
                     successfully, word is truncated to the offset at  command
                     completion.   <>;word  cannot  be  used with the exec(2).
                     built-in.

       <<[-]word     The shell input is read up to a line that is the same  as
                     word after any quoting has been removed, or to an end-of-
                     file.  No parameter substitution,  command  substitution,
                     arithmetic  substitution  or file name generation is per-
                     formed on word.  The resulting document, called  a  here-
                     document,  becomes  the standard input.  If any character
                     of word is quoted, then no interpretation is placed  upon
                     the  characters  of  the  document;  otherwise, parameter
                     expansion, command substitution, and arithmetic substitu-
                     tion  occur,  \new-line is ignored, and \ must be used to
                     quote the characters \, $, `.  If - is  appended  to  <<,
                     then all leading tabs are stripped from word and from the
                     document.  If # is appended to <<,  then  leading  spaces
                     and tabs will be stripped off the first line of the docu-
                     ment and up to an equivalent indentation will be stripped
                     from  the  remaining  lines and from word.  A tab stop is
                     assumed to occur at every 8 columns for the  purposes  of
                     determining the indentation.

       <<<word       A  short  form of here document in which word becomes the
                     contents of the here-document after any parameter  expan-
                     sion,  command  substitution, and arithmetic substitution
                     occur.

       <&digit       The standard input is  duplicated  from  file  descriptor
                     digit  (see  dup(2)).   Similarly for the standard output
                     using >&digit.

       <&digit-      The file descriptor given by digit is moved  to  standard
                     input.  Similarly for the standard output using >&digit-.

       <&-           The standard input is closed.  Similarly for the standard
                     output using >&-.

       <&p           The input from the co-process is moved to standard input.

       >&p           The output to the co-process is moved to standard output.

       <#((expr))    Evaluate arithmetic expression  expr  and  position  file
                     descriptor  0 to the resulting value bytes from the start
                     of the file.  The variables CUR and EOF evaluate  to  the
                     current  offset  and end-of-file offset respectively when
                     evaluating expr.

       >#((offset))  The same as <# except applies to file descriptor 1.

       <#pattern     Seeks forward to the beginning of the next line  contain-
                     ing pattern.

       <##pattern    The  same  as <# except that the portion of the file that
                     is skipped is copied to standard output.

       If one of the above is preceded by a digit, with no intervening  space,
       then  the  file  descriptor number referred to is that specified by the
       digit (instead of the default 0 or 1).  If one of the above, other than
       >&- and the ># and <# forms, is preceded by {varname} with no interven-
       ing space, then a file descriptor number > 10 will be selected  by  the
       shell  and stored in the variable varname.  If >&- or the any of the >#
       and <# forms is preceded by {varname} the value of varname defines  the
       file descriptor to close or position.  For example:

              ... 2>&1

       means  file  descriptor 2 is to be opened for writing as a duplicate of
       file descriptor 1 and

              exec {n}<file

       means open file named file for reading and store  the  file  descriptor
       number in variable n.

       The  order  in  which  redirections  are specified is significant.  The
       shell evaluates each redirection in  terms  of  the  (file  descriptor,
       file) association at the time of evaluation.  For example:

              ... 1>fname 2>&1

       first associates file descriptor 1 with file fname.  It then associates
       file descriptor 2 with the file associated with file descriptor 1 (i.e.
       fname).   If the order of redirections were reversed, file descriptor 2
       would be associated with the terminal (assuming file descriptor  1  had
       been) and then file descriptor 1 would be associated with file fname.

       If  a  command is followed by & and job control is not active, then the
       default standard input for the command is  the  empty  file  /dev/null.
       Otherwise,  the environment for the execution of a command contains the
       file descriptors of the invoking  shell  as  modified  by  input/output
       specifications.

   Environment.
       The  environment (see environ(7)) is a list of name-value pairs that is
       passed to an executed program in the same  way  as  a  normal  argument
       list.   The  names  must  be  identifiers  and the values are character
       strings.  The shell interacts with the environment in several ways.  On
       invocation,  the shell scans the environment and creates a variable for
       each name found, giving it the corresponding value and  attributes  and
       marking  it export.  Executed commands inherit the environment.  If the
       user modifies the values of these variables or creates new ones,  using
       the export or typeset -x commands, they become part of the environment.
       The environment seen by any executed command is thus  composed  of  any
       name-value pairs originally inherited by the shell, whose values may be
       modified by the current shell, plus any additions which must  be  noted
       in export or typeset -x commands.

       The  environment for any simple-command or function may be augmented by
       prefixing it with one or more variable assignments.  A variable assign-
       ment argument is a word of the form identifier=value.  Thus:

              TERM=450 cmd args                  and
              (export TERM; TERM=450; cmd args)

       are  equivalent  (as  far  as  the  above execution of cmd is concerned
       except for special built-in commands listed below - those that are pre-
       ceded with a dagger).

       If the obsolete -k option is set, all variable assignment arguments are
       placed in the environment, even if they occur after the  command  name.
       The following first prints a=b c and then c:

              echo a=b c
              set -k
              echo a=b c
       This  feature  is  intended for use with scripts written for early ver-
       sions of the shell and its use in new scripts is strongly  discouraged.
       It is likely to disappear someday.

   Functions.
       For  historical  reasons,  there  are two ways to define functions, the
       name() syntax and the function name syntax, described in  the  Commands
       section  above.   Shell  functions  are  read in and stored internally.
       Alias names are resolved when the function is read.  Functions are exe-
       cuted like commands with the arguments passed as positional parameters.
       (See Execution below.)

       Functions defined by the function name syntax and called by  name  exe-
       cute  in the same process as the caller and share all files and present
       working directory with the caller.  Traps  caught  by  the  caller  are
       reset  to  their  default action inside the function.  A trap condition
       that is not caught or ignored by the function causes  the  function  to
       terminate  and  the condition to be passed on to the caller.  A trap on
       EXIT set inside a function is executed in the environment of the caller
       after the function completes.  Ordinarily, variables are shared between
       the calling program and the function.   However,  the  typeset  special
       built-in  command  used within a function defines local variables whose
       scope includes the current function.  They can be passed  to  functions
       that  they  call in the variable assignment list that precedes the call
       or as arguments passed as name  references.   Errors  within  functions
       return control to the caller.

       Functions defined with the name() syntax and functions defined with the
       function name syntax that are invoked with the .  special built-in  are
       executed  in the caller's environment and share all variables and traps
       with the caller.  Errors within these  function  executions  cause  the
       script that contains them to abort.

       The  special  built-in  command  return is used to return from function
       calls.

       Function names can be listed with the -f or +f option  of  the  typeset
       special  built-in command.  The text of functions, when available, will
       also be listed with -f.  Functions can be undefined with the -f  option
       of the unset special built-in command.

       Ordinarily, functions are unset when the shell executes a shell script.
       Functions that need to be defined across separate  invocations  of  the
       shell  should  be  placed  in a directory and the FPATH variable should
       contain the name of this directory.  They may also be specified in  the
       ENV file.

   Discipline Functions.
       Each  variable  can  have  zero or more discipline functions associated
       with it.  The shell initially understands  the  discipline  names  get,
       set,  append,  and  unset but can be added when defining new types.  On
       most systems others can be added at run  time  via  the  C  programming
       interface  extension  provided by the builtin built-in utility.  If the
       get discipline is defined for a variable, it is  invoked  whenever  the
       given  variable is referenced.  If the variable .sh.value is assigned a
       value inside the discipline  function,  the  referenced  variable  will
       evaluate to this value instead.  If the set discipline is defined for a
       variable, it is invoked whenever  the  given  variable  is  assigned  a
       value.   If  the  append  discipline  is  defined for a variable, it is
       invoked whenever a value is appended to the given variable.  The  vari-
       able  .sh.value  is given the value of the variable before invoking the
       discipline, and the variable will be assigned the  value  of  .sh.value
       after  the discipline completes.  If .sh.value is unset inside the dis-
       cipline, then that value is unchanged.   If  the  unset  discipline  is
       defined  for  a  variable, it is invoked whenever the given variable is
       unset.  The variable will not be unset unless it  is  unset  explicitly
       from within this discipline function.

       The  variable  .sh.name contains the name of the variable for which the
       discipline function is called, .sh.subscript is the  subscript  of  the
       variable,  and  .sh.value  will contain the value being assigned inside
       the set discipline function.  The variable _  is  a  reference  to  the
       variable  including  the  subscript  if  any.   For the set discipline,
       changing .sh.value will change the value that gets assigned.   Finally,
       the  expansion  ${var.name}, when name is the name of a discipline, and
       there is no variable of this name, is equivalent to the command substi-
       tution ${ var.name;}.


   Name Spaces.
       Commands  and  functions  that  are  executed  as part of the list of a
       namespace command that modify variables or create new  ones,  create  a
       new variable whose name is the name of the name space as given by iden-
       tifier preceded by ..  When a variable whose name  is  name  is  refer-
       enced,  it  is first searched for using .identifier.name.  Similarly, a
       function defined by a command in the namespace list  is  created  using
       the name space name  preceded by a ..

       When  the list of a namespace command contains a namespace command, the
       names of variables and functions that are created consist of the  vari-
       able or function name preceded by the list of identifiers each preceded
       by ..

       Outside of a name space, a variable or function created inside  a  name
       space can be referenced by preceding it with the name space name.

       By default, variables staring with .sh are in the sh name space.


   Type Variables.
       Typed  variables provide a way to create data structure and objects.  A
       type can be defined either by a shared library, by  the  enum  built-in
       command  described  below, or by using the new -T option of the typeset
       built-in command.  With the -T option of typeset, the type name, speci-
       fied  as  an  option  argument  to  -T, is set with a compound variable
       assignment that defines the  type.   Function  definitions  can  appear
       inside  the  compound  variable  assignment and these become discipline
       functions for this type  and  can  be  invoked  or  redefined  by  each
       instance  of  the type.  The function name create is treated specially.
       It is invoked for each instance of the type that is created but is  not
       inherited and cannot be redefined for each instance.

       When  a  type  is  defined  a  special built-in command of that name is
       added.  These built-ins are declaration commands and  follow  the  same
       expansion rules as all the special built-in commands defined below that
       are preceded by .  These commands can subsequently be used inside  fur-
       ther  type  definitions.  The man page for these commands can be gener-
       ated by using the --man option or any of the other -- options described
       with  getopts.   The -r, -a, -A, -h, and -S options of typeset are per-
       mitted with each of these new built-ins.

       An instance of a type is created by invoking the type name followed  by
       one  or  more instance names.  Each instance of the type is initialized
       with a copy of the sub-variables  except  for  sub-variables  that  are
       defined  with  the -S option.  Variables defined with the -S are shared
       by all instances of the type.  Each instance can change  the  value  of
       any  sub-variable  and  can also define new discipline functions of the
       same names as those defined by the type definition as well as any stan-
       dard  discipline names.  No additional sub-variables can be defined for
       any instance.

       When defining a type, if the value of a sub-variable is not set and the
       -r  attribute is specified, it causes the sub-variable to be a required
       sub-variable.  Whenever an instance of a type is created, all  required
       sub-variables  must  be specified.  These sub-variables become readonly
       in each instance.

       When unset is invoked on a sub-variable  within  a  type,  and  the  -r
       attribute  has not been specified for this field, the value is reset to
       the default value associative with the type.  Invoking unset on a  type
       instance  not  contained  within another type deletes all sub-variables
       and the variable itself.

       A type definition can be derived from another type definition by defin-
       ing  the first sub-variable name as _ and defining its type as the base
       type.  Any remaining definitions will be  additions  and  modifications
       that  apply  to the new type.  If the new type name is the same is that
       of the base type, the type will be replaced and the original type  will
       no longer be accessible.

       The typeset command with the -T and no option argument or operands will
       write all the type definitions to standard output in a form  that  that
       can be read in to create all they types.

   Jobs.
       If  the  monitor option of the set command is turned on, an interactive
       shell associates a job with each pipeline.  It keeps a table of current
       jobs,  printed by the jobs command, and assigns them small integer num-
       bers.  When a job is started asynchronously with &, the shell prints  a
       line which looks like:

            [1] 1234

       indicating that the job which was started asynchronously was job number
       1 and had one (top-level) process, whose process id was 1234.

       This paragraph and the next require features that are not in  all  ver-
       sions  of UNIX and may not apply.  If you are running a job and wish to
       do something else you may hit the key ^Z (control-Z) which sends a STOP
       signal  to the current job.  The shell will then normally indicate that
       the job has been `Stopped', and print another  prompt.   You  can  then
       manipulate the state of this job, putting it in the background with the
       bg command, or run some other commands and then  eventually  bring  the
       job  back  into  the  foreground  with the foreground command fg.  A ^Z
       takes effect immediately and is like an interrupt in that pending  out-
       put and unread input are discarded when it is typed.

       A  job  being  run in the background will stop if it tries to read from
       the terminal.  Background jobs are normally allowed to produce  output,
       but this can be disabled by giving the command stty tostop.  If you set
       this tty option, then background jobs will stop when they try  to  pro-
       duce output like they do when they try to read input.

       A  job pool is a collection of jobs started with list & associated with
       a name.

       There are several ways to refer to jobs in the shell.   A  job  can  be
       referred  to  by  the process id of any process of the job or by one of
       the following:
       %number
              The job with the given number.
       pool   All the jobs in the job pool named by pool.
       pool.number
              The job number number in the job pool named by pool.
       %string
              Any job whose command line begins with string.
       %?string
              Any job whose command line contains string.
       %%     Current job.
       %+     Equivalent to %%.
       %-     Previous job.  In addition, unless noted otherwise,  wherever  a
              job  can  be specified, the name of a background job pool can be
              used to represent all the jobs in that pool.

       The shell learns immediately whenever a process changes state.  It nor-
       mally  informs  you  whenever  a job becomes blocked so that no further
       progress is possible, but only just before it prints a prompt.  This is
       done  so  that  it  does  not  otherwise disturb your work.  The notify
       option of the set command causes the shell to print  these  job  change
       messages as soon as they occur.

       When the monitor option is on, each background job that completes trig-
       gers any trap set for CHLD.

       When you try to leave the shell while jobs are running or stopped,  you
       will  be warned that `You have stopped(running) jobs.'  You may use the
       jobs command to see what they are.  If  you  immediately  try  to  exit
       again,  the shell will not warn you a second time, and the stopped jobs
       will be terminated.  When a login shell receives a HUP signal, it sends
       a  HUP  signal  to  each job that has not been disowned with the disown
       built-in command described below.

   Signals.
       The INT and QUIT signals for an invoked command are ignored if the com-
       mand is followed by & and the monitor option is not active.  Otherwise,
       signals have the values inherited by the shell from its parent (but see
       also the trap built-in command below).

   Execution.
       Each  time  a command is read, the above substitutions are carried out.
       If the command name matches one of the Special Built-in Commands listed
       below, it is executed within the current shell process.  Next, the com-
       mand name is checked to see if it matches a user defined function.   If
       it  does,  the  positional  parameters  are saved and then reset to the
       arguments of the function call.  A function is  also  executed  in  the
       current shell process.  When the function completes or issues a return,
       the positional parameter list is restored.  For functions defined  with
       the  function  name syntax, any trap set on EXIT within the function is
       executed.  The exit value of a function is the value of the  last  com-
       mand  executed.  If a command name is not a special built-in command or
       a user defined function, but it is one of the built-in commands  listed
       below, it is executed in the current shell process.

       The  shell  variables  PATH  followed by the variable FPATH defines the
       list of directories to search for the command name.  Alternative direc-
       tory  names  are  separated  by  a  colon  (:).   The  default  path is
       /bin:/usr/bin: (specifying /bin, /usr/bin, and the current directory in
       that  order).   The  current  directory can be specified by two or more
       adjacent colons, or by a colon at the beginning  or  end  of  the  path
       list.   If  the  command name contains a /, then the search path is not
       used.  Otherwise, each directory in the list of directories defined  by
       PATH and FPATH is checked in order.  If the directory being searched is
       contained in FPATH and contains a file whose name matches  the  command
       being  searched,  then this file is loaded into the current shell envi-
       ronment as if it were the argument to the . command  except  that  only
       preset  aliases  are expanded, and a function of the given name is exe-
       cuted as described above.

       If this directory is not in FPATH the shell  first  determines  whether
       there is a built-in version of a command corresponding to a given path-
       name and if so it is invoked in the current process.  If no built-in is
       found,  the shell checks for a file named .paths in this directory.  If
       found and there is a line of the form FPATH=path where  path  names  an
       existing  directory  then  that directory is searched after immediately
       after the current directory as if it were found in the FPATH  variable.
       If path does not begin with /, it is checked for relative to the direc-
       tory being searched.

       The .paths file is then checked  for a line of the form PLUGIN_LIB=lib-
       name  [  :  libname  ]  ...  .   Each  library named by libname will be
       searched for as if it were an option argument to builtin -f, and if  it
       contains a built-in of the specified name this will be executed instead
       of a command by this name.  Any built-in loaded from  a  library  found
       this  way  will  be associated with the directory containing the .paths
       file so it will only execute if not found in an earlier directory.

       Finally, the directory will be checked for a file of  the  given  name.
       If  the  file  has  execute  permission but is not an a.out file, it is
       assumed to be a file containing shell commands.  A  separate  shell  is
       spawned  to  read  it.   All non-exported variables are removed in this
       case.  If the shell command file doesn't have read  permission,  or  if
       the  setuid and/or setgid bits are set on the file, then the shell exe-
       cutes an agent whose job it is to set up the  permissions  and  execute
       the  shell with the shell command file passed down as an open file.  If
       the .paths contains a line of the form name=value in the first or  sec-
       ond  line, then the environment variable name is modified by prepending
       the directory specified by value to the directory list.   If  value  is
       not  an  absolute  directory, then it specifies a directory relative to
       the directory that the executable was found.  If the environment  vari-
       able  name  does  not already exist it will be added to the environment
       list for the specified command.  A parenthesized command is executed in
       a sub-shell without removing non-exported variables.

   Command Re-entry.
       The  text  of  the  last HISTSIZE (default 512) commands entered from a
       terminal device is saved in a history file.  The file $HOME/.sh_history
       is  used if the HISTFILE variable is not set or if the file it names is
       not writable.  A shell can  access  the  commands  of  all  interactive
       shells which use the same named HISTFILE.  The built-in command hist is
       used to list or edit a portion of this file.  The portion of  the  file
       to be edited or listed can be selected by number or by giving the first
       character or characters of the command.  A single command or  range  of
       commands  can be specified.  If you do not specify an editor program as
       an argument to hist then the value of the variable  HISTEDIT  is  used.
       If  HISTEDIT is unset, the obsolete variable FCEDIT is used.  If FCEDIT
       is not defined, then /bin/ed is used.  The edited command(s) is printed
       and  re-executed  upon leaving the editor unless you quit without writ-
       ing.  The -s option (and in obsolete versions, the editor  name  -)  is
       used  to skip the editing phase and to re-execute the command.  In this
       case a substitution parameter of the form old=new can be used to modify
       the  command  before  execution.  For example, with the preset alias r,
       which is aliased to 'hist -s', typing `r bad=good  c'  will  re-execute
       the  most  recent command which starts with the letter c, replacing the
       first occurrence of the string bad with the string good.

   In-line Editing Options.
       Normally, each command line entered from a terminal  device  is  simply
       typed  followed by a new-line (`RETURN' or `LINE FEED').  If either the
       emacs, gmacs, or vi option is active, the user  can  edit  the  command
       line.   To  be  in  either  of  these  edit modes set the corresponding
       option.  An editing option is automatically selected each time the VIS-
       UAL  or  EDITOR  variable is assigned a value ending in either of these
       option names.

       The editing features require that the user's terminal  accept  `RETURN'
       as  carriage return without line feed and that a space (` ') must over-
       write the current character on the screen.

       Unless the multiline option is on, the editing modes implement  a  con-
       cept  where  the  user is looking through a window at the current line.
       The window width is the value of COLUMNS if it  is  defined,  otherwise
       80.   If  the window width is too small to display the prompt and leave
       at least 8 columns to enter input, the prompt  is  truncated  from  the
       left.  If the line is longer than the window width minus two, a mark is
       displayed at the end of the window to notify the user.  As  the  cursor
       moves  and  reaches  the  window boundaries the window will be centered
       about the cursor.  The mark is a > (<, *) if the line  extends  on  the
       right (left, both) side(s) of the window.

       The  search  commands  in  each edit mode provide access to the history
       file.  Only strings are matched, not patterns, although a leading ^  in
       the  string  restricts the match to begin at the first character in the
       line.

       Each of the edit modes has an operation to list the files  or  commands
       that match a partially entered word.  When applied to the first word on
       the line, or the first word after a ;, |, &, or (, and  the  word  does
       not  begin  with  ~ or contain a /, the list of aliases, functions, and
       executable commands defined by the PATH variable that could  match  the
       partial word is displayed.  Otherwise, the list of files that match the
       given word is displayed.  If the partially entered word does  not  con-
       tain  any  file expansion characters, a * is appended before generating
       these lists.  After displaying the generated list, the  input  line  is
       redrawn.   These  operations  are  called command name listing and file
       name listing, respectively.  There are additional operations,  referred
       to  as  command name completion and file name completion, which compute
       the list of matching commands or files, but  instead  of  printing  the
       list,  replace  the current word with a complete or partial match.  For
       file name completion, if the match is unique, a / is  appended  if  the
       file is a directory and a space is appended if the file is not a direc-
       tory.  Otherwise, the longest common prefix for all the matching  files
       replaces  the  word.   For command name completion, only the portion of
       the file names after the last / are used to find  the  longest  command
       prefix.   If  only  a single name matches this prefix, then the word is
       replaced with the command name followed by a space.  When using  a  tab
       for  completion  that  does  not yield a unique match, a subsequent tab
       will provide a numbered list  of  matching  alternatives.   A  specific
       selection  can  be  made by entering the selection number followed by a
       tab.

   Key Bindings.
       The KEYBD trap can be used to intercept keys  as  they  are  typed  and
       change  the  characters that are actually seen by the shell.  This trap
       is executed after each character (or sequence of  characters  when  the
       first  character is ESC) is entered while reading from a terminal.  The
       variable .sh.edchar contains the character or character sequence  which
       generated  the  trap.   Changing  the  value  of .sh.edchar in the trap
       action causes the shell to behave as if the new value were entered from
       the keyboard rather than the original value.

       The  variable .sh.edcol is set to the input column number of the cursor
       at the time of the input.  The variable .sh.edmode is set to  ESC  when
       in  vi  insert  mode  (see below) and is null otherwise.  By prepending
       ${.sh.editmode} to a value assigned to .sh.edchar  it  will  cause  the
       shell to change to control mode if it is not already in this mode.

       This trap is not invoked for characters entered as arguments to editing
       directives, or while reading input for a character search.

   Emacs Editing Mode.
       This mode is entered by enabling either the emacs or gmacs option.  The
       only  difference between these two modes is the way they handle ^T.  To
       edit, the user moves the cursor to the  point  needing  correction  and
       then inserts or deletes characters or words as needed.  All the editing
       commands are control characters or escape sequences.  The notation  for
       control  characters  is caret (^) followed by the character.  For exam-
       ple, ^F is the notation for control F.  This is entered  by  depressing
       `f'  while  holding  down the `CTRL' (control) key.  The `SHIFT' key is
       not depressed.  (The notation ^?  indicates the DEL (delete) key.)

       The notation for escape sequences is M- followed by a  character.   For
       example,  M-f  (pronounced  Meta f) is entered by depressing ESC (ascii
       033) followed by `f'.  (M-F would be the notation for ESC  followed  by
       `SHIFT' (capital) `F'.)

       All  edit  commands operate from any place on the line (not just at the
       beginning).  Neither the `RETURN' nor the `LINE FEED'  key  is  entered
       after edit commands except when noted.

       ^F        Move cursor forward (right) one character.
       M-[C      Move cursor forward (right) one character.
       M-f       Move  cursor forward one word.  (The emacs editor's idea of a
                 word is a string of characters consisting  of  only  letters,
                 digits and underscores.)
       ^B        Move cursor backward (left) one character.
       M-[D      Move cursor backward (left) one character.
       M-b       Move cursor backward one word.
       ^A        Move cursor to start of line.
       M-[H      Move cursor to start of line.
       ^E        Move cursor to end of line.
       M-[Y      Move cursor to end of line.
       ^]char    Move cursor forward to character char on current line.
       M-^]char  Move cursor backward to character char on current line.
       ^X^X      Interchange the cursor and mark.
       erase     (User  defined erase character as defined by the stty(1) com-
                 mand, usually ^H or #.)  Delete previous character.
       lnext     (User defined  literal  next  character  as  defined  by  the
                 stty(1)  command,  or  ^V  if not defined.)  Removes the next
                 character's editing features (if any).
       ^D        Delete current character.
       M-d       Delete current word.
       M-^H      (Meta-backspace) Delete previous word.
       M-h       Delete previous word.
       M-^?      (Meta-DEL) Delete previous word (if your interrupt  character
                 is ^?  (DEL, the default) then this command will not work).
       ^T        Transpose  current  character  with  previous  character  and
                 advance the cursor in emacs  mode.   Transpose  two  previous
                 characters in gmacs mode.
       ^C        Capitalize current character.
       M-c       Capitalize current word.
       M-l       Change the current word to lower case.
       ^K        Delete  from  the cursor to the end of the line.  If preceded
                 by a numerical parameter whose value is less than the current
                 cursor  position,  then  delete from given position up to the
                 cursor.  If preceded by a numerical parameter whose value  is
                 greater  than  the  current cursor position, then delete from
                 cursor up to given cursor position.
       ^W        Kill from the cursor to the mark.
       M-p       Push the region from the cursor to the mark on the stack.
       kill      (User defined kill character as defined by the stty  command,
                 usually ^G or @.)  Kill the entire current line.  If two kill
                 characters are entered in  succession,  all  kill  characters
                 from  then on cause a line feed (useful when using paper ter-
                 minals).
       ^Y        Restore last item removed from line. (Yank item back  to  the
                 line.)
       ^L        Line feed and print current line.
       M-^L      Clear the screen.
       ^@        (Null character) Set mark.
       M-space   (Meta space) Set mark.
       ^J        (New line) Execute the current line.
       ^M        (Return) Execute the current line.
       eof       End-of-file  character,  normally ^D, is processed as an End-
                 of-file only if the current line is null.
       ^P        Fetch previous command.  Each time ^P is entered the previous
                 command  back  in time is accessed.  Moves back one line when
                 not on the first line of a multi-line command.
       M-[A      If the cursor is at the end of the line, it is equivalent  to
                 ^R with string set to the contents of the current line.  Oth-
                 erwise, it is equivalent to ^P.
       M-<       Fetch the least recent (oldest) history line.
       M->       Fetch the most recent (youngest) history line.
       ^N        Fetch next command line.  Each time ^N is  entered  the  next
                 command line forward in time is accessed.
       M-[B      Equivalent to ^N.
       ^Rstring  Reverse search history for a previous command line containing
                 string.  If a parameter of zero is given, the search is  for-
                 ward.   String is terminated by a `RETURN' or `NEW LINE'.  If
                 string is preceded by a ^, the matched line must  begin  with
                 string.   If  string  is  omitted, then the next command line
                 containing the most recent string is accessed.  In this  case
                 a parameter of zero reverses the direction of the search.
       ^O        Operate  -  Execute  the current line and fetch the next line
                 relative to current line from the history file.
       M-digits  (Escape) Define numeric parameter, the digits are taken as  a
                 parameter  to  the  next command.  The commands that accept a
                 parameter are ^F, ^B, erase, ^C, ^D, ^K, ^R, ^P, ^N, ^], M-.,
                 M-^], M-_, M-=, M-b, M-c, M-d, M-f, M-h, M-l and M-^H.
       M-letter  Soft-key  -  Your  alias list is searched for an alias by the
                 name _letter and if an alias of this  name  is  defined,  its
                 value  will  be inserted on the input queue.  The letter must
                 not be one of the above meta-functions.
       M-[letter Soft-key - Your alias list is searched for an  alias  by  the
                 name  __letter  and  if an alias of this name is defined, its
                 value will be inserted on the input queue.  This can be  used
                 to program function keys on many terminals.
       M-.       The  last  word  of  the  previous command is inserted on the
                 line.  If preceded by a numeric parameter, the value of  this
                 parameter  determines  which  word  to insert rather than the
                 last word.
       M-_       Same as M-..
       M-*       Attempt file name generation on the current word.  An  aster-
                 isk is appended if the word doesn't match any file or contain
                 any special pattern characters.
       M-ESC     Command or file name completion as described above.
       ^I tab    Attempts command or file name completion as described  above.
                 If a partial completion occurs, repeating this will behave as
                 if M-= were entered.  If no match is found or  entered  after
                 space, a tab is inserted.
       M-=       If not preceded by a numeric parameter, it generates the list
                 of matching commands or file names as described above.   Oth-
                 erwise,  the  word  under  the cursor is replaced by the item
                 corresponding to the value of the numeric parameter from  the
                 most  recently generated command or file list.  If the cursor
                 is not on a word, it is inserted instead.
       ^U        Multiply parameter of next command by 4.
       \         Escape next character.  Editing characters, the user's erase,
                 kill  and  interrupt (normally ^?)  characters may be entered
                 in a command line or in a search string if preceded by  a  \.
                 The \ removes the next character's editing features (if any).
       M-^V      Display version of the shell.
       M-#       If  the  line does not begin with a #, a # is inserted at the
                 beginning of the line and after each new-line, and  the  line
                 is entered.  This causes a comment to be inserted in the his-
                 tory file.  If the line begins with a #, the # is deleted and
                 one # after each new-line is also deleted.

   Vi Editing Mode.
       There  are  two  typing modes.  Initially, when you enter a command you
       are in the input mode.  To edit, the user enters control mode by typing
       ESC (033) and moves the cursor to the point needing correction and then
       inserts or deletes characters or words as needed.   Most  control  com-
       mands accept an optional repeat count prior to the command.

       When  in  vi  mode  on  most systems, canonical processing is initially
       enabled and the command will be echoed again if the speed is 1200  baud
       or greater and it contains any control characters or less than one sec-
       ond has elapsed since the prompt was printed.  The ESC character termi-
       nates  canonical  processing  for  the remainder of the command and the
       user can then modify the command line.  This scheme has the  advantages
       of canonical processing with the type-ahead echoing of raw mode.

       If  the option viraw is also set, the terminal will always have canoni-
       cal processing disabled.  This mode is implicit for systems that do not
       support  two  alternate  end of line delimiters, and may be helpful for
       certain terminals.

        Input Edit Commands
              By default the editor is in input mode.
              erase     (User defined erase character as defined by  the  stty
                        command, usually ^H or #.)  Delete previous character.
              ^W        Delete  the  previous  blank  separated word.  On some
                        systems the viraw option may be required for  this  to
                        work.
              eof       As the first character of the line causes the shell to
                        terminate unless the ignoreeof option is set.   Other-
                        wise this character is ignored.
              lnext     (User defined literal next character as defined by the
                        stty(1) or ^V if not defined.)  Removes the next char-
                        acter's  editing  features  (if any).  On some systems
                        the viraw option may be required for this to work.
              \         Escape the next erase or kill character.
              ^I tab    Attempts command or file name completion as  described
                        above and returns to input mode.  If a partial comple-
                        tion occurs, repeating this will behave as if  =  were
                        entered  from  control  mode.  If no match is found or
                        entered after space, a tab is inserted.
        Motion Edit Commands
              These commands will move the cursor.
              [count]l  Cursor forward (right) one character.
              [count][C Cursor forward (right) one character.
              [count]w  Cursor forward one alpha-numeric word.
              [count]W  Cursor to the beginning of the next word that  follows
                        a blank.
              [count]e  Cursor to end of word.
              [count]E  Cursor to end of the current blank delimited word.
              [count]h  Cursor backward (left) one character.
              [count][D Cursor backward (left) one character.
              [count]b  Cursor backward one word.
              [count]B  Cursor to preceding blank separated word.
              [count]|  Cursor to column count.
              [count]fc Find the next character c in the current line.
              [count]Fc Find the previous character c in the current line.
              [count]tc Equivalent to f followed by h.
              [count]Tc Equivalent to F followed by l.
              [count];  Repeats  count  times,  the last single character find
                        command, f, F, t, or T.
              [count],  Reverses the last single character find command  count
                        times.
              0         Cursor to start of line.
              ^         Cursor to start of line.
              [H        Cursor to first non-blank character in line.
              $         Cursor to end of line.
              [Y        Cursor to end of line.
              %         Moves  to balancing (, ), {, }, [, or ].  If cursor is
                        not on one of the above characters, the  remainder  of
                        the  line  is searched for the first occurrence of one
                        of the above characters first.
        Search Edit Commands
              These commands access your command history.
              [count]k  Fetch previous command.  Each time k  is  entered  the
                        previous command back in time is accessed.
              [count]-  Equivalent to k.
              [count][A If  cursor  is at the end of the line it is equivalent
                        to / with string^set to the contents  of  the  current
                        line.  Otherwise, it is equivalent to k.
              [count]j  Fetch  next  command.  Each time j is entered the next
                        command forward in time is accessed.
              [count]+  Equivalent to j.
              [count][B Equivalent to j.
              [count]G  The command number count is fetched.  The  default  is
                        the least recent history command.
              /string   Search backward through history for a previous command
                        containing string.  String is terminated by a `RETURN'
                        or  `NEW LINE'.   If  string  is  preceded by a ^, the
                        matched line must begin with  string.   If  string  is
                        null, the previous string will be used.
              ?string   Same  as  /  except that search will be in the forward
                        direction.
              n         Search for next match of the last pattern to  /  or  ?
                        commands.
              N         Search  for  next match of the last pattern to / or ?,
                        but in reverse direction.
        Text Modification Edit Commands
              These commands will modify the line.
              a         Enter input mode and  enter  text  after  the  current
                        character.
              A         Append text to the end of the line.  Equivalent to $a.
              [count]cmotion
              c[count]motion
                        Delete  current  character  through the character that
                        motion would move the cursor to and enter input  mode.
                        If  motion  is  c, the entire line will be deleted and
                        input mode entered.
              C         Delete the current character through the end  of  line
                        and enter input mode.  Equivalent to c$.
              S         Equivalent to cc.
              [count]s  Replace characters under the cursor in input mode.
              D         Delete  the current character through the end of line.
                        Equivalent to d$.
              [count]dmotion
              d[count]motion
                        Delete current character through  the  character  that
                        motion  would  move  to.   If motion is d , the entire
                        line will be deleted.
              i         Enter input mode and insert text  before  the  current
                        character.
              I         Insert text before the beginning of the line.  Equiva-
                        lent to 0i.
              [count]P  Place the previous text modification before  the  cur-
                        sor.
              [count]p  Place the previous text modification after the cursor.
              R         Enter  input mode and replace characters on the screen
                        with characters you type overlay fashion.
              [count]rc Replace the count character(s) starting at the current
                        cursor position with c, and advance the cursor.
              [count]x  Delete current character.
              [count]X  Delete preceding character.
              [count].  Repeat the previous text modification command.
              [count]~  Invert  the case of the count character(s) starting at
                        the current cursor position and advance the cursor.
              [count]_  Causes the count word of the previous  command  to  be
                        appended  and  input  mode  entered.  The last word is
                        used if count is omitted.
              *         Causes an * to be appended to  the  current  word  and
                        file name generation attempted.  If no match is found,
                        it rings the bell.  Otherwise, the word is replaced by
                        the matching pattern and input mode is entered.
              \         Command or file name completion as described above.
        Other Edit Commands
              Miscellaneous commands.
              [count]ymotion
              y[count]motion
                        Yank  current  character through character that motion
                        would move the cursor to and puts them into the delete
                        buffer.  The text and cursor are unchanged.
              yy        Yanks the entire line.
              Y         Yanks  from  current position to end of line.  Equiva-
                        lent to y$.
              u         Undo the last text modifying command.
              U         Undo all the text modifying commands performed on  the
                        line.
              [count]v  Returns  the  command hist -e ${VISUAL:-${EDITOR:-vi}}
                        count in the input buffer.  If count is omitted,  then
                        the current line is used.
              ^L        Line  feed and print current line.  Has effect only in
                        control mode.
              ^J        (New line) Execute the  current  line,  regardless  of
                        mode.
              ^M        (Return) Execute the current line, regardless of mode.
              #         If  the  first  character  of the command is a #, then
                        this command deletes this # and each # that follows  a
                        newline.   Otherwise, sends the line after inserting a
                        # in front of each line in the  command.   Useful  for
                        causing the current line to be inserted in the history
                        as a comment  and  uncommenting  previously  commented
                        commands in the history file.
              [count]=  If  count  is  not specified, it generates the list of
                        matching commands or file names  as  described  above.
                        Otherwise,  the  word under the the cursor is replaced
                        by the count item from  the  most  recently  generated
                        command or file list.  If the cursor is not on a word,
                        it is inserted instead.
              @letter   Your alias list is searched for an alias by  the  name
                        _letter  and  if an alias of this name is defined, its
                        value will be inserted on the input queue for process-
                        ing.
              ^V        Display version of the shell.

   Built-in Commands.
       The  following  simple-commands  are  executed  in  the  shell process.
       Input/Output redirection is permitted.  Unless otherwise indicated, the
       output  is written on file descriptor 1 and the exit status, when there
       is no syntax error, is zero.  Except for :, true, false, echo,  newgrp,
       and  login, all built-in commands accept -- to indicate end of options.
       They also interpret the option --man as a request to  display  the  man
       page onto standard error and -?  as a help request which prints a usage
       message on standard error.  Commands that are preceded by  one  or  two
       symbols  are special built-in commands and are treated specially in the
       following ways:
       1.     Variable assignment lists preceding the command remain in effect
              when the command completes.
       2.     I/O redirections are processed after variable assignments.
       3.     Errors cause a script that contains them to abort.
       4.     They are not valid function names.
       5.     Words  following a command preceded by that are in the format of
              a variable assignment are expanded with  the  same  rules  as  a
              variable assignment.  This means that tilde substitution is per-
              formed after the = sign and field splitting and file name gener-
              ation  are  not  performed.  These are called declaration built-
              ins.

        : [ arg ... ]
              The command only expands parameters.

        . name [ arg ... ]
              If name is a function defined with the  function  name  reserved
              word syntax, the function is executed in the current environment
              (as if it had been defined with the name()  syntax.)   Otherwise
              if  name  refers to a file, the file is read in its entirety and
              the commands are executed in the current shell environment.  The
              search path specified by PATH is used to find the directory con-
              taining the file.  If any arguments arg are given,  they  become
              the  positional  parameters  while processing the .  command and
              the original positional parameters are restored upon completion.
              Otherwise  the  positional  parameters  are unchanged.  The exit
              status is the exit status of the last command executed.

        alias [ -ptx ]  [ name[ =value  ] ] ...
              alias with no arguments prints the list of aliases in  the  form
              name=value  on  standard  output.  The -p option causes the word
              alias to be inserted before each one.  When one  or  more  argu-
              ments  are  given, an alias is defined for each name whose value
              is given.  A trailing space in value causes the next word to  be
              checked  for alias substitution.  The obsolete -t option is used
              to set and list tracked aliases.  The value of a  tracked  alias
              is the full pathname corresponding to the given name.  The value
              becomes undefined when the value of PATH is reset but the  alias
              remains  tracked.   Without  the -t option, for each name in the
              argument list for which no value is given, the name and value of
              the  alias  is  printed.   The obsolete -x option has no effect.
              The exit status is non-zero if a name is given,  but  no  value,
              and no alias has been defined for the name.

       bg [ job... ]
              This  command is only on systems that support job control.  Puts
              each specified job into the background.  The current job is  put
              in  the  background  if  job  is  not specified.  See Jobs for a
              description of the format of job.

        break [ n ]
              Exit from the enclosing for, while, until, or  select  loop,  if
              any.  If n is specified, then break n levels.

       builtin [ -ds ] [ -f file ] [ name ... ]
              If  name  is  not  specified, and no -f option is specified, the
              built-ins are printed on standard output.  The -s option  prints
              only the special built-ins.  Otherwise, each name represents the
              pathname whose basename is the name of the built-in.  The  entry
              point function name is determined by prepending b_ to the built-
              in name.  A built-in specified by a pathname will only  be  exe-
              cuted  when that pathname would be found during the path search.
              Built-ins found in libraries loaded via the .paths file will  be
              associate  with  the  pathname  of  the directory containing the
              .paths file.

       The ISO C/C++ prototype is b_mycommand(int  argc,  char  *argv[],  void
       *context)  for  the builtin command mycommand where argv is array an of
       argc elements and context is an optional pointer to a Shell_t structure
       as described in <ast/shell.h>.
       Special  built-ins  cannot  be  bound to a pathname or deleted.  The -d
       option deletes each of the given built-ins.  On  systems  that  support
       dynamic  loading,  the  -f option names a shared library containing the
       code for built-ins.  The shared library  prefix  and/or  suffix,  which
       depend  on  the  system, can be omitted.  Once a library is loaded, its
       symbols become available for subsequent invocations of builtin.  Multi-
       ple libraries can be specified with separate invocations of the builtin
       command.  Libraries are searched in the reverse order in which they are
       specified.   When  a  library is loaded, it looks for a function in the
       library whose name is lib_init() and  invokes  this  function  with  an
       argument of 0.

       cd [ -LP ] [ arg ]
       cd [ -LP ] old new
              This  command  can be in either of two forms.  In the first form
              it changes the current directory to arg.  If arg is - the direc-
              tory  is  changed to the previous directory.  The shell variable
              HOME is the default arg.  The variable PWD is set to the current
              directory.   The  shell  variable CDPATH defines the search path
              for the directory containing arg.  Alternative  directory  names
              are separated by a colon (:).  The default path is <null> (spec-
              ifying the current directory).  Note that the current  directory
              is  specified  by a null path name, which can appear immediately
              after the equal sign or between the  colon  delimiters  anywhere
              else  in  the path list.  If arg begins with a / then the search
              path is not used.  Otherwise, each  directory  in  the  path  is
              searched for arg.
              The  second form of cd substitutes the string new for the string
              old in the current directory name, PWD, and tries to  change  to
              this new directory.
              By default, symbolic link names are treated literally when find-
              ing the directory name.  This is equivalent to  the  -L  option.
              The  -P  option causes symbolic links to be resolved when deter-
              mining the directory.  The last instance of -L or -P on the com-
              mand line determines which method is used.
              The cd command may not be executed by rksh.  rksh93.

       command [ -pvxV ] name [ arg ... ]
              Without  the  -v  or  -V options, command executes name with the
              arguments given by arg.  The -p option causes a default path  to
              be  searched  rather  than the one defined by the value of PATH.
              Functions will not be searched for when finding name.  In  addi-
              tion,  if name refers to a special built-in, none of the special
              properties associated with the leading daggers will be  honored.
              (For  example, the predefined alias redirect='command exec' pre-
              vents a script from terminating when an invalid  redirection  is
              given.)   With  the -x option, if command execution would result
              in a failure because there are too many arguments, errno  E2BIG,
              the  shell will invoke command name multiple times with a subset
              of the arguments on each invocation.  Arguments that occur prior
              to  the  first word that expands to multiple arguments and after
              the last word that expands to multiple arguments will be  passed
              on each invocation.  The exit status will be the maximum invoca-
              tion exit status.  With the -v option, command is equivalent  to
              the  built-in  whence  command  described  below.  The -V option
              causes command to act like whence -v.

        continue [ n ]
              Resume the next iteration of the enclosing for, while, until, or
              select loop.  If n is specified, then resume at the n-th enclos-
              ing loop.

       disown [ job... ]
              Causes the shell not to send a HUP signal to each given job,  or
              all  active  jobs  if  job is omitted, when a login shell termi-
              nates.

       echo [ arg ... ]
              When the first arg does not begin with a  -,  and  none  of  the
              arguments  contain  a  \, then echo prints each of its arguments
              separated by a space and terminated by a  new-line.   Otherwise,
              the  behavior  of  echo  is system dependent and print or printf
              described below should be  used.   See  echo(1)  for  usage  and
              description.

        enum [ -i  ] type[=(value ...) ]
              Creates a declaration command named type that is an integer type
              that allows one of the specified values  as  enumeration  names.
              If  =(value ...)  is omitted, then type must be an indexed array
              variable with at least two elements and  the  values  are  taken
              from  this  array  variable.   If -i is specified the values are
              case insensitive.

        eval [ arg ... ]
              The arguments are read as input to the shell and  the  resulting
              command(s) executed.

        exec [ -c ] [ -a name ] [ arg ... ]
              If  arg is given, the command specified by the arguments is exe-
              cuted in place of this shell without  creating  a  new  process.
              The -c option causes the environment to be cleared before apply-
              ing variable assignments associated with  the  exec  invocation.
              The  -a  option causes name rather than the first arg, to become
              argv[0] for the new process.  Input/output arguments may  appear
              and affect the current process.  If arg is not given, the effect
              of this command is to modify file descriptors as  prescribed  by
              the  input/output  redirection  list.   In  this  case, any file
              descriptor numbers greater than 2  that  are  opened  with  this
              mechanism are closed when invoking another program.

        exit [ n ]
              Causes  the  shell  to exit with the exit status specified by n.
              The value will be the least significant 8 bits of the  specified
              status.   If  n  is omitted, then the exit status is that of the
              last command executed.  An end-of-file will also cause the shell
              to  exit  except for a shell which has the ignoreeof option (see
              set below) turned on.

        export [ -p ] [ name[=value] ] ...
              If name is not given, the names and values of each variable with
              the  export  attribute  are  printed with the values quoted in a
              manner that allows them to be re-input.  The export  command  is
              the  same  as  typeset -x except that if you use export within a
              function, no local variable is created.  The  -p  option  causes
              the  word export to be inserted before each one.  Otherwise, the
              given names are marked for automatic export to  the  environment
              of subsequently-executed commands.

       false  Does nothing, and exits 1. Used with until for infinite loops.

       fg [ job... ]
              This  command is only on systems that support job control.  Each
              job specified is brought to the foreground and waited for in the
              specified order.  Otherwise, the current job is brought into the
              foreground.  See Jobs for a description of the format of job.

       getconf [ name [ pathname ] ]
              Prints the current value of the configuration parameter given by
              name.   The  configuration  parameters  are  defined by the IEEE
              POSIX 1003.1 and IEEE POSIX 1003.2 standards.  (See  pathconf(2)
              and  sysconf(2).)  The pathname argument is required for parame-
              ters whose value depends on the location in the file system.  If
              no  arguments  are given, getconf prints the names and values of
              the current configuration parameters.  The pathname  /  is  used
              for each of the parameters that requires pathname.

       getopts [  -a name ] optstring vname [ arg ... ]
              Checks arg for legal options.  If arg is omitted, the positional
              parameters are used.  An option argument begins with a + or a -.
              An  option not beginning with + or - or the argument -- ends the
              options.  Options beginning with + are only recognized when opt-
              string  begins  with  a  +.  optstring contains the letters that
              getopts recognizes.  If a letter is followed by a :, that option
              is  expected  to have an argument.  The options can be separated
              from the argument by blanks.  The option -?  causes  getopts  to
              generate a usage message on standard error.  The -a argument can
              be used to specify the name to use for the usage message,  which
              defaults to $0.
              getopts  places  the next option letter it finds inside variable
              vname each time it  is  invoked.   The  option  letter  will  be
              prepended  with  a + when arg begins with a +.  The index of the
              next arg is stored in OPTIND.  The option argument, if any, gets
              stored in OPTARG.
              A  leading  : in optstring causes getopts to store the letter of
              an invalid option in OPTARG, and to  set  vname  to  ?   for  an
              unknown option and to : when a required option argument is miss-
              ing.  Otherwise, getopts prints an error message.  The exit sta-
              tus is non-zero when there are no more options.
              There is no way to specify any of the options :, +, -, ?, [, and
              ].  The option # can only be specified as the first option.

       hist [ -e ename  ] [ -nlr ] [ first [ last ] ]
       hist -s  [ old=new ] [ command ]
              In the first form, a range of commands from  first  to  last  is
              selected  from the last HISTSIZE commands that were typed at the
              terminal.  The arguments first and last may be  specified  as  a
              number  or  as  a  string.   A string is used to locate the most
              recent command starting with the given string.  A negative  num-
              ber  is used as an offset to the current command number.  If the
              -l option is selected, the commands are listed on standard  out-
              put.   Otherwise,  the editor program ename is invoked on a file
              containing these keyboard commands.  If ename is  not  supplied,
              then the value of the variable HISTEDIT is used.  If HISTEDIT is
              not set, then FCEDIT (default /bin/ed) is used  as  the  editor.
              When  editing  is complete, the edited command(s) is executed if
              the changes have been saved.  If last is not specified, then  it
              will be set to first.  If first is not specified, the default is
              the previous command for  editing  and  -16  for  listing.   The
              option  -r  reverses the order of the commands and the option -n
              suppresses command numbers when listing.  In  the  second  form,
              command  is interpreted as first described above and defaults to
              the last command executed.  The resulting  command  is  executed
              after the optional substitution old=new is performed.

       jobs [ -lnp ] [ job ... ]
              Lists  information  about  each given job; or all active jobs if
              job is omitted.  The -l option lists process ids in addition  to
              the  normal  information.  The -n option only displays jobs that
              have stopped or exited  since  last  notified.   The  -p  option
              causes  only  the  process  group  to be listed.  See Jobs for a
              description of the format of job.

       kill [ -s signame ] job ...
       kill [ -n signum ] job ...
       kill -Ll [ sig ... ]
              Sends either the TERM (terminate) signal or the specified signal
              to the specified jobs or processes.  Signals are either given by
              number with the -n option or by name  with  the  -s  option  (as
              given  in  <signal.h>,  stripped  of the prefix ``SIG'' with the
              exception that SIGCLD is named CHLD).  For backward  compatibil-
              ity,  the  n  and s can be omitted and the number or name placed
              immediately after the -.  If the signal being sent is TERM (ter-
              minate)  or HUP (hangup), then the job or process will be sent a
              CONT (continue) signal if it is stopped.  The argument  job  can
              be  the  process  id of a process that is not a member of one of
              the active jobs.  See Jobs for a description of  the  format  of
              job.   In  the  third  form,  kill -l, or kill -L, if sig is not
              specified, the signal names are listed.  The -l option list only
              the  signal names.  -L options lists each signal name and corre-
              sponding number.  Otherwise, for each sig that is  a  name,  the
              corresponding  signal  number is listed.  For each sig that is a
              number, the signal name corresponding to the least significant 8
              bits of sig is listed.

       let arg ...
              Each  arg  is  a separate arithmetic expression to be evaluated.
              let only recognizes octal constants starting with 0 when the set
              option  letoctal  is on.  See Arithmetic Evaluation above, for a
              description of arithmetic expression evaluation.
              The exit status is 0 if the value of the last expression is non-
              zero, and 1 otherwise.

        newgrp [ arg ... ]
              Equivalent to exec /bin/newgrp arg ....

       print [ -CRenprsv ] [ -u unit] [ -f format ] [ arg ... ]
              With  no  options or with option - or --, each arg is printed on
              standard output.  The -f  option  causes  the  arguments  to  be
              printed  as  described  by printf.  In this case, any e, n, r, R
              options are ignored.  Otherwise, unless the -C, -R,  -r,  or  -v
              are specified, the following escape conventions will be applied:
              \a     The alert character (ascii 07).
              \b     The backspace character (ascii 010).
              \c     Causes print to end without processing more arguments and
                     not adding a new-line.
              \f     The formfeed character (ascii 014).
              \n     The new-line character (ascii 012).
              \r     The carriage return character (ascii 015).
              \t     The tab character (ascii 011).
              \v     The vertical tab character (ascii 013).
              \E     The escape character (ascii 033).
              \\     The backslash character \.
              \0x    The character defined by  the  1,  2,  or  3-digit  octal
                     string given by x.

              The  -R  option  will print all subsequent arguments and options
              other than -n.  The -e causes the above escape conventions to be
              applied.   This is the default behavior.  It reverses the effect
              of an earlier -r.  The -p option  causes  the  arguments  to  be
              written  onto the pipe of the process spawned with |& instead of
              standard output.  The -v option treats each arg  as  a  variable
              name  and  writes  the  value  in  the printf %B format.  The -C
              option treats each arg as a variable name and writes  the  value
              in the printf %#B format.  The -s option causes the arguments to
              be written onto the history file  instead  of  standard  output.
              The -u option can be used to specify a one digit file descriptor
              unit number unit on  which  the  output  will  be  placed.   The
              default is 1.  If the option -n is used, no new-line is added to
              the output.

       printf format [ arg ... ]
              The arguments arg are printed on standard output  in  accordance
              with  the  ANSI-C  formatting  rules  associated with the format
              string format.  If the number of arguments exceeds the number of
              format  specifications,  the  format  string is reused to format
              remaining arguments.  The following extensions can also be used:
              %b     A %b format can be used instead of  %s  to  cause  escape
                     sequences  in  the  corresponding  arg  to be expanded as
                     described in print.
              %B     A %B option causes each of the arguments to be treated as
                     variable  names  and the binary value of variable will be
                     printed.  The alternate flag # causes a compound variable
                     to  be  output on a single line.  This is most useful for
                     compound variables and variables whose attribute is -b.
              %H     A %H format can be used instead of %s to cause characters
                     in  arg  that are special in HTML and XML to be output as
                     their entity name.  The alternate flag # formats the out-
                     put for use as a URI.
              %P     A  %P format can be used instead of %s to cause arg to be
                     interpreted as an  extended  regular  expression  and  be
                     printed as a shell pattern.
              %R     A  %R format can be used instead of %s to cause arg to be
                     interpreted as a shell pattern and to be  printed  as  an
                     extended regular expression.
              %q     A  %q  format  can  be  used  instead  of %s to cause the
                     resulting string to be quoted in a  manner  than  can  be
                     reinput to the shell.  When q is preceded by the alterna-
                     tive format specifier, #, the string is quoted in  manner
                     suitable as a field in a .csv format file.
              %(date-format)T
                     A  %(date-format)T format can be use to treat an argument
                     as a date/time string and to format the date/time accord-
                     ing  to  the  date-format as defined for the date(1) com-
                     mand.
              %Z     A %Z format will output a byte whose value is 0.
              %d     The precision field of the %d format can be followed by a
                     .  and the output base.  In this case, the # flag charac-
                     ter causes base# to be prepended.
              #      The # flag, when used with the %d format without an  out-
                     put base, displays the output in powers of 1000 indicated
                     by one of the following suffixes: k M G T P E,  and  when
                     used  with the %i format displays the output in powers of
                     1024 indicated by one of the following suffixes: Ki Mi Gi
                     Ti Pi Ei.
              =      The  = flag centers the output within the specified field
                     width.
              L      The L flag, when used with the %c or %s  formats,  treats
                     precision as character width instead of byte count.
              ,      The  ,  flag,  when used with the %d or %f formats, sepa-
                     rates groups of digits with the grouping delimiter (,  on
                     groups of 3 in the C locale.)

       pwd [ -LP ]
              Outputs  the  value  of  the  current working directory.  The -L
              option is the default; it prints the logical name of the current
              directory.   If  the  -P option is given, all symbolic links are
              resolved from the name.  The last instance of -L or  -P  on  the
              command line determines which method is used.

       read  [  -ACSprsv  ] [ -d delim] [ -n n] [ [ -N n] [ [ -t timeout] [ -u
       unit] [ vname?prompt ] [ vname ... ]
              The shell input mechanism.  One line is read and  is  broken  up
              into  fields  using  the  characters  in IFS as separators.  The
              escape character, \, is used to remove any special  meaning  for
              the  next  character  and  for line continuation.  The -d option
              causes the read to continue to  the  first  character  of  delim
              rather  than  new-line.  The -n option causes at most n bytes to
              read rather a full line but will return when reading from a slow
              device  as soon as any characters have been read.  The -N option
              causes exactly n to be  read  unless  an  end-of-file  has  been
              encountered  or the read times out because of the -t option.  In
              raw mode, -r, the \ character is  not  treated  specially.   The
              first  field is assigned to the first vname, the second field to
              the second vname, etc., with leftover  fields  assigned  to  the
              last vname.  When vname has the binary attribute and -n or -N is
              specified, the bytes that are read are stored directly into  the
              variable.   If  the -v is specified, then the value of the first
              vname will be used as a default value when reading from a termi-
              nal device.  The -A option causes the variable vname to be unset
              and each field that is read to be stored in successive  elements
              of  the  indexed array vname.  The -C option causes the variable
              vname to be read as a compound variable.  Blanks will be ignored
              when  finding  the  beginning  open  parenthesis.  The -S option
              causes the line to be treated like a record  in  a  .csv  format
              file  so  that  double quotes can be used to allow the delimiter
              character and the new-line character to appear within  a  field.
              The  -p  option causes the input line to be taken from the input
              pipe of a process spawned by the shell  using  |&.   If  the  -s
              option  is  present, the input will be saved as a command in the
              history file.  The option -u can be used to specify a one  digit
              file descriptor unit unit to read from.  The file descriptor can
              be opened with the exec special built-in command.   The  default
              value  of unit n is 0.  The option -t is used to specify a time-
              out in seconds when reading from a terminal or pipe.   If  vname
              is omitted, then REPLY is used as the default vname.  An end-of-
              file with the -p option causes cleanup for this process so  that
              another can be spawned.  If the first argument contains a ?, the
              remainder of this word is used as a  prompt  on  standard  error
              when  the  shell is interactive.  The exit status is 0 unless an
              end-of-file is encountered or read has timed out.

        readonly [ -p ] [ vname[=value] ] ...
              If vname is not given, the names and  values  of  each  variable
              with the readonly attribute is printed with the values quoted in
              a manner that allows them to  be  re-inputted.   The  -p  option
              causes the word readonly to be inserted before each one.  Other-
              wise, the given vnames are marked readonly and these names  can-
              not  be changed by subsequent assignment.  When defining a type,
              if the value of a readonly sub-variable is not defined the value
              is required when creating each instance.

        return [ n ]
              Causes  a  shell function or .  script to return to the invoking
              script with the exit status specified by n.  The value  will  be
              the  least  significant 8 bits of the specified status.  If n is
              omitted, then the return status is that of the last command exe-
              cuted.   If  return  is  invoked  while not in a function or a .
              script, then it behaves the same as exit.

        set [ +-BCGabefhkmnoprstuvx ] [ +-o [ option ] ] ... [ +-A vname ]   [
       arg ... ]
              The options for this command have meaning as follows:
              -A      Array  assignment.   Unset the variable vname and assign
                      values sequentially from the arg list.  If +A  is  used,
                      the variable vname is not unset first.
              -B      Enable  brace  pattern  field  generation.   This is the
                      default behavior.
              -B      Enable brace group expansion.  On by default.
              -C      Prevents redirection > from truncating  existing  files.
                      Files  that are created are opened with the O_EXCL mode.
                      Requires >| to truncate a file when turned on.
              -G      Causes the pattern ** by itself to match files and  zero
                      or  more  directories  and sub-directories when used for
                      file name generation.  If followed by a / only  directo-
                      ries and sub-directories are matched.
              -a      All  subsequent variables that are defined are automati-
                      cally exported.
              -b      Prints job completion messages as soon as  a  background
                      job  changes  state  rather  than  waiting  for the next
                      prompt.
              -e      Unless contained in a || or && command, or  the  command
                      following  an  if while or until command or in the pipe-
                      line following !, if a command has a non-zero exit  sta-
                      tus,  execute the ERR trap, if set, and exit.  This mode
                      is disabled while reading profiles.
              -f      Disables file name generation.
              -h      Each command becomes a tracked alias when first  encoun-
                      tered.
              -k      (Obsolete). All variable assignment arguments are placed
                      in the environment for a command, not  just  those  that
                      precede the command name.
              -m      Background jobs will run in a separate process group and
                      a line will print upon completion.  The exit  status  of
                      background jobs is reported in a completion message.  On
                      systems with job control, this option is turned on auto-
                      matically for interactive shells.
              -n      Read  commands  and check them for syntax errors, but do
                      not execute them.  Ignored for interactive shells.
              -o      The following argument  can  be  one  of  the  following
                      option names:
                      allexport
                              Same as -a.
                      errexit Same as -e.
                      bgnice  All background jobs are run at a lower priority.
                              This is the default mode.
                      braceexpand
                              Same as -B.
                      emacs   Puts you in an emacs style  in-line  editor  for
                              command entry.
                      globstar
                              Same as -G.
                      gmacs   Puts  you  in  a  gmacs style in-line editor for
                              command entry.
                      ignoreeof
                              The shell will not  exit  on  end-of-file.   The
                              command exit must be used.
                      keyword Same as -k.
                      letoctal
                              The  let command allows octal constants starting
                              with 0.
                      markdirs
                              All directory names  resulting  from  file  name
                              generation have a trailing / appended.
                      monitor Same as -m.
                      multiline
                              The  built-in editors will use multiple lines on
                              the screen for lines that are  longer  than  the
                              width  of the screen.  This may not work for all
                              terminals.
                      noclobber
                              Same as -C.
                      noexec  Same as -n.
                      noglob  Same as -f.
                      nolog   Do not save function definitions in the  history
                              file.
                      notify  Same as -b.
                      nounset Same as -u.
                      pipefail
                              A  pipeline  will  not complete until all compo-
                              nents of the pipeline have  completed,  and  the
                              return  value will be the value of the last non-
                              zero command to fail or zero if no  command  has
                              failed.
                      showme  When  enabled, simple commands or pipelines pre-
                              ceded by a semicolon (;) will be displayed as if
                              the  xtrace  option were enabled but will not be
                              executed.  Otherwise,  the  leading  ;  will  be
                              ignored.
                      privileged
                              Same as -p.
                      verbose Same as -v.
                      trackall
                              Same as -h.
                      vi      Puts  you  in  insert mode of a vi style in-line
                              editor until you hit the escape  character  033.
                              This  puts  you in control mode.  A return sends
                              the line.
                      viraw   Each character is processed as it is typed in vi
                              mode.
                      xtrace  Same as -x.
                      If  no  option name is supplied, then the current option
                      settings are printed.
              -p      Disables processing of the $HOME/.profile file and  uses
                      the  file  /etc/suid_profile  instead  of  the ENV file.
                      This mode is on whenever the effective uid (gid) is  not
                      equal  to  the  real uid (gid).  Turning this off causes
                      the effective uid and gid to be set to the real uid  and
                      gid.
              -r      Enables  the  restricted  shell.   This option cannot be
                      unset once set.
              -s      Sort the positional parameters lexicographically.
              -t      (Obsolete).  Exit after reading and executing  one  com-
                      mand.
              -u      Treat unset parameters as an error when substituting.
              -v      Print shell input lines as they are read.
              -x      Print commands and their arguments as they are executed.
              --      Do  not  change any of the options; useful in setting $1
                      to a value beginning with -.   If  no  arguments  follow
                      this option then the positional parameters are unset.

              As an obsolete feature, if the first arg is - then the -x and -v
              options are turned off and the next arg is treated as the  first
              argument.   Using  +  rather  than  - causes these options to be
              turned off.  These options can also be used upon  invocation  of
              the  shell.   The  current  set  of  options may be found in $-.
              Unless -A is specified, the remaining arguments  are  positional
              parameters  and  are  assigned,  in  order, to $1 $2 ....  If no
              arguments are given, then the names and values of all  variables
              are printed on the standard output.

        shift [ n ]
              The  positional  parameters  from $n+1 ...  are renamed $1 ... ,
              default n is 1.  The parameter n can be any  arithmetic  expres-
              sion  that evaluates to a non-negative number less than or equal
              to $#.

       sleep seconds
              Suspends execution for the number of decimal  seconds  or  frac-
              tions of a second given by seconds.

        trap [ -p ] [ action ] [ sig ] ...
              The  -p  option causes the trap action associated with each trap
              as specified by the arguments to  be  printed  with  appropriate
              quoting.   Otherwise,  action will be processed as if it were an
              argument to eval when the shell receives  signal(s)  sig.   Each
              sig can be given as a number or as the name of the signal.  Trap
              commands are executed in order of signal number.  Any attempt to
              set  a trap on a signal that was ignored on entry to the current
              shell is ineffective.  If action is omitted and the first sig is
              a  number,  or if action is -, then the trap(s) for each sig are
              reset to their original values.  If action is  the  null  string
              then  this signal is ignored by the shell and by the commands it
              invokes.  If sig is ERR then action will be executed whenever  a
              command has a non-zero exit status.  If sig is DEBUG then action
              will be executed before each command.  The variable  .sh.command
              will  contain  the  contents  of  the  current command line when
              action is running.  If the exit status of the trap is 2 the com-
              mand  will  not  be executed.  If the exit status of the trap is
              255 and inside a function or a dot script, the function  or  dot
              script  will return.  If sig is 0 or EXIT and the trap statement
              is executed inside the body of a function defined with the func-
              tion  name syntax, then the command action is executed after the
              function completes.  If sig is 0 or EXIT for a trap set  outside
              any  function  then  the command action is executed on exit from
              the shell.  If sig is KEYBD, then action will be executed  when-
              ever  a key is read while in emacs, gmacs, or vi mode.  The trap
              command with no arguments prints a list of  commands  associated
              with each signal number.

       An  exit  or  return without an argument in a trap action will preserve
       the exit status of the command that invoked the trap.

       true   Does nothing, and exits 0. Used with while for infinite loops.

        typeset [ +-ACHSfblmnprtux ] [ +-EFLRXZi[n] ]   [ +-M  [ mapname ] ] [
       -T  [ tname=(assign_list) ] ] [ -h str ] [ -a [type] ] [ vname[=value ]
        ] ...
              Sets attributes and values for shell  variables  and  functions.
              When  invoked  inside  a function defined with the function name
              syntax, a new instance of the variable vname is created, and the
              variable's  value  and  type are restored when the function com-
              pletes.  The following list of attributes may be specified:
              -A     Declares vname to be an  associative  array.   Subscripts
                     are strings rather than arithmetic expressions.
              -C     causes each vname to be a compound variable.  value names
                     a compound variable it is copied into vname.   Otherwise,
                     it unsets each vname.
              -a     Declares vname to be an indexed array.  If type is speci-
                     fied, it must be the name of an enumeration type  created
                     with the enum command and it allows enumeration constants
                     to be used as subscripts.
              -E     Declares vname to be a double  precision  floating  point
                     number.   If n is non-zero, it defines the number of sig-
                     nificant figures that  are  used  when  expanding  vname.
                     Otherwise, ten significant figures will be used.
              -F     Declares  vname  to  be a double precision floating point
                     number.  If n is  non-zero,  it  defines  the  number  of
                     places after the decimal point that are used when expand-
                     ing vname.  Otherwise ten places after the decimal  point
                     will be used.
              -H     This  option  provides  UNIX to host-name file mapping on
                     non-UNIX machines.
              -L     Left justify and remove leading blanks from value.  If  n
                     is non-zero, it defines the width of the field, otherwise
                     it is determined by the  width  of  the  value  of  first
                     assignment.   When  the  variable  is  assigned to, it is
                     filled on the right with blanks or truncated,  if  neces-
                     sary,  to  fit  into  the field.  The -R option is turned
                     off.
              -M     Use the character mapping mapping defined by  wctrans(3).
                     such  as  tolower  and  toupper when assigning a value to
                     each of the specified operands.  When mapping  is  speci-
                     fied  and  there are not operands, all variables that use
                     this mapping are written to standard output.   When  map-
                     ping  is  omitted  and  there are no operands, all mapped
                     variables are written to standard output.
              -R     Right justify and fill with leading blanks.  If n is non-
                     zero,  it defines the width of the field, otherwise it is
                     determined by the width of the value of first assignment.
                     The  field  is  left filled with blanks or truncated from
                     the end if the variable is reassigned.  The -L option  is
                     turned off.
              -S     When used within the assign_list of a type definition, it
                     causes the specified sub-variable to  be  shared  by  all
                     instances  of  the  type.   When  used  inside a function
                     defined with the function reserved  word,  the  specified
                     variables  will  have  function static scope.  Otherwise,
                     the variable is unset prior to processing the  assignment
                     list.
              -T     If  followed  by  tname, it creates a type named by tname
                     using the compound assignment assign_list to tname.  Oth-
                     erwise,  it  writes  all the type definitions to standard
                     output.
              -X     Declares vname to be a double  precision  floating  point
                     number  and expands using the %a format of ISO-C99.  If n
                     is non-zero, it defines the number of  hex  digits  after
                     the  radix  point that is used when expanding vname.  The
                     default is 10.
              -Z     Right justify and fill with leading zeros  if  the  first
                     non-blank  character is a digit and the -L option has not
                     been set.  Remove leading zeros if the -L option is  also
                     set.   If  n  is  non-zero,  it  defines the width of the
                     field, otherwise it is determined by  the  width  of  the
                     value of first assignment.
              -f     The  names  refer  to function names rather than variable
                     names.  No assignments can be made  and  the  only  other
                     valid  options are -S, -t, -u and -x.  The -S can be used
                     with discipline functions defined in a type  to  indicate
                     that  the function is static.  For a static function, the
                     same method will be used by all instances of that type no
                     matter which instance references it.  In addition, it can
                     only use value of variables from the original type  defi-
                     nition.   These  discipline functions cannot be redefined
                     in any type instance.  The -t option turns  on  execution
                     tracing  for  this  function.   The -u option causes this
                     function to be marked undefined.  The FPATH variable will
                     be  searched  to  find  the  function definition when the
                     function is referenced.  If no options other than  -f  is
                     specified, then the function definition will be displayed
                     on standard output.  If +f is specified, then a line con-
                     taining  the  function  name  followed by a shell comment
                     containing the line number and  path  name  of  the  file
                     where  this  function  was defined, if any, is displayed.
                     The exit status can be  used  to  determine  whether  the
                     function is defined so that typeset -f .sh.math.name will
                     return 0 when math function name is defined and  non-zero
                     otherwise.
              -b     The  variable  can hold any number of bytes of data.  The
                     data can be text or binary.  The value is represented  by
                     the  base64  encoding  of the data.  If -Z is also speci-
                     fied, the size in bytes of the data in the buffer will be
                     determined  by  the  size associated with the -Z.  If the
                     base64 string assigned results in more data, it  will  be
                     truncated.  Otherwise, it will be filled with bytes whose
                     value is zero.  The printf format %B can be used to  out-
                     put  the actual data in this buffer instead of the base64
                     encoding of the data.
              -h     Used within type definitions to add information when gen-
                     erating  information  about  the  sub-variable on the man
                     page.  It is ignored when used outside of a type  defini-
                     tion.   When  used  with -f the information is associated
                     with the corresponding discipline function.
              -i     Declares vname to be represented internally  as  integer.
                     The  right  hand side of an assignment is evaluated as an
                     arithmetic expression when assigning to an integer.  If n
                     is  non-zero, it defines the output arithmetic base, oth-
                     erwise the output base will be ten.
              -l     Used with -i, -E or -F, to indicate long integer, or long
                     float.   Otherwise,  all  upper-case  characters are con-
                     verted to lower-case.   The  upper-case  option,  -u,  is
                     turned off.  Equivalent to -M tolower .
              -m     moves  or renames the variable.  The value is the name of
                     a variable whose value will be moved to vname.  The orig-
                     inal  variable  will  be  unset.  Cannot be used with any
                     other options.
              -n     Declares vname to be a reference to  the  variable  whose
                     name  is defined by the value of variable vname.  This is
                     usually used to reference a variable  inside  a  function
                     whose  name  has  been  passed as an argument.  Cannot be
                     used with any other options.
              -p     The name, attributes and values for the given vnames  are
                     written  on standard output in a form that can be used as
                     shell input.  If +p is specified, then the values are not
                     displayed.
              -r     The given vnames are marked readonly and these names can-
                     not be changed by subsequent assignment.
              -t     Tags the variables.  Tags are user definable and have  no
                     special meaning to the shell.
              -u     When  given  along  with  -i, specifies unsigned integer.
                     Otherwise, all lower-case  characters  are  converted  to
                     upper-case.   The  lower-case  option, -l, is turned off.
                     Equivalent to -M toupper .
              -x     The given vnames are marked for automatic export  to  the
                     environment of subsequently-executed commands.  Variables
                     whose names contain a .  cannot be exported.

              The -i attribute cannot be specified along with -R, -L,  -Z,  or
              -f.

              Using + rather than - causes these options to be turned off.  If
              no vname arguments are given, a list of vnames  (and  optionally
              the values) of the variables is printed.  (Using + rather than -
              keeps the values from being  printed.)   The  -p  option  causes
              typeset followed by the option letters to be printed before each
              name rather than the names of the options.  If any option  other
              than  -p  is  given,  only those variables which have all of the
              given options are printed.  Otherwise, the vnames and attributes
              of all variables that have attributes are printed.

       ulimit [ -HSacdfmnpstv ] [ limit ]
              Set  or display a resource limit.  The available resource limits
              are listed below.  Many systems do not support one  or  more  of
              these  limits.   The  limit for a specified resource is set when
              limit is specified.  The value of limit can be a number  in  the
              unit specified below with each resource, or the value unlimited.
              The -H and -S options specify whether the hard limit or the soft
              limit  for  the  given  resource is set.  A hard limit cannot be
              increased once it is set.  A soft limit can be increased  up  to
              the  value  of the hard limit.  If neither the H nor S option is
              specified, the limit applies  to  both.   The  current  resource
              limit  is printed when limit is omitted.  In this case, the soft
              limit is printed unless H is  specified.   When  more  than  one
              resource  is  specified, then the limit name and unit is printed
              before the value.
              -a     Lists all of the current resource limits.
              -c     The number of 512-byte blocks on the size of core dumps.
              -d     The number of K-bytes on the size of the data area.
              -f     The number of 512-byte blocks on files that can be  writ-
                     ten  by  the current process or by child processes (files
                     of any size may be read).
              -m     The number of K-bytes on the size of physical memory.
              -n     The number of file descriptors plus 1.
              -p     The number of 512-byte blocks for pipe buffering.
              -s     The number of K-bytes on the size of the stack area.
              -t     The number of CPU seconds to be used by each process.
              -v     The number of K-bytes for virtual memory.

              If no option is given, -f is assumed.

       umask [ -S ] [ mask ]
              The user file-creation mask is set to mask (see umask(2)).  mask
              can  either  be an octal number or a symbolic value as described
              in chmod(1).  If a symbolic value is given, the new umask  value
              is  the complement of the result of applying mask to the comple-
              ment of the previous umask value.  If mask is omitted, the  cur-
              rent  value  of  the  mask is printed.  The -S option causes the
              mode to be printed as a symbolic value.  Otherwise, the mask  is
              printed in octal.

        unalias [ -a ] name ...
              The  aliases  given  by  the  list of names are removed from the
              alias list.  The -a option causes all the aliases to be unset.

       unset [ -fnv ] vname ...
              The variables given by the list of vnames are unassigned,  i.e.,
              except  for  sub-variables  within  a  type,  their  values  and
              attributes are erased.  For sub-variables of a type, the  values
              are  reset to the default value from the type definition.  Read-
              only variables cannot be unset.  If the -f option is  set,  then
              the  names  refer  to  function names.  If the -v option is set,
              then the names refer to variable names.  The -f option overrides
              -v.   If  -n is set and name is a name reference, then name will
              be unset rather than  the  variable  that  it  references.   The
              default  is  equivalent  to  -v.   Unsetting  LINENO, MAILCHECK,
              OPTARG, OPTIND, RANDOM, SECONDS, TMOUT, and _ removes their spe-
              cial meaning even if they are subsequently assigned to.

       wait [ job ... ]
              Wait  for  the  specified job and report its termination status.
              If job is not given, then all currently active  child  processes
              are  waited  for.   The exit status from this command is that of
              the last process waited for if job is specified; otherwise it is
              zero.  See Jobs for a description of the format of job.

       whence [ -afpv ] name ...
              For each name, indicate how it would be interpreted if used as a
              command name.
              The -v option produces a more verbose  report.   The  -f  option
              skips  the  search  for  functions.   The  -p option does a path
              search for name even if name is  an  alias,  a  function,  or  a
              reserved  word.   The -p option turns off the -v option.  The -a
              option is similar to the -v option but  causes  all  interpreta-
              tions of the given name to be reported.

   Invocation.
       If the shell is invoked by exec(2), and the first character of argument
       zero ($0) is -, then the shell is assumed to be a login shell and  com-
       mands  are  read from /etc/profile and then from either .profile in the
       current directory or $HOME/.profile, if either file exists.  Next,  for
       interactive shells, commands are read from the file named by performing
       parameter expansion, command substitution, and arithmetic  substitution
       on  the  value  of the environment variable ENV if the file exists.  If
       the -s option is not present and arg and a file  by  the  name  of  arg
       exists,  then  it  reads  and  executes this script.  Otherwise, if the
       first arg does not contain a /, a path search is performed on the first
       arg  to  determine  the  name of the script to execute.  The script arg
       must have execute permission and any setuid and setgid settings will be
       ignored.   If  the script is not found on the path, arg is processed as
       if it named a built-in command or function.  Commands are then read  as
       described  below;  the  following  options are interpreted by the shell
       when it is invoked:

       -D      Do not execute the script, but output the set of double  quoted
               strings  preceded  by a $.  These strings are needed for local-
               ization of the script to different locales.
       -E      Reads the file named by the ENV variable or by $HOME/.kshrc  if
               not defined after the profiles.
       -c        If  the -c option is present, then commands are read from the
                 first arg.  Any remaining arguments become positional parame-
                 ters starting at 0.
       -s        If  the  -s option is present or if no arguments remain, then
                 commands are read from the  standard  input.   Shell  output,
                 except  for  the output of the Special Commands listed above,
                 is written to file descriptor 2.
       -i        If the -i option is present or if the shell input and  output
                 are  attached  to  a terminal (as told by tcgetattr(2)), then
                 this shell is interactive.  In this case TERM is ignored  (so
                 that  kill  0 does not kill an interactive shell) and INTR is
                 caught and ignored (so that wait is ).  In all cases, QUIT is
                 ignored by the shell.
       -r        If the -r option is present, the shell is a restricted shell.
       -D        A  list of all double quoted strings that are preceded by a $
                 will be printed on standard output and the shell  will  exit.
                 This  set  of strings will be subject to language translation
                 when the locale is not C or POSIX.  No commands will be  exe-
                 cuted.

       -P        If  -P or -o profile is present, the shell is a profile shell
                 (see pfexec(1)).

       -R filename
                 The -R filename option is used to generate a cross  reference
                 database that can be used by a separate utility to find defi-
                 nitions and references for variables and commands.

       The remaining options and arguments are described under the set command
       above.  An optional - as the first argument is ignored.

   Rksh Only.
       Rksh  is  used  to  set up login names and execution environments whose
       capabilities are more controlled than those of the standard shell.  The
       actions  of rksh are identical to those of ksh, except that the follow-
       ing are disallowed:
              Unsetting the restricted option.
              changing directory (see cd(1)),
              setting or unsetting the value  or  attributes  of  SHELL,  ENV,
              FPATH, or PATH,
              specifying path or command names containing /,
              redirecting output (>, >|, <>, and >>).
              adding or deleting built-in commands.
              using command -p to invoke a command.

       The  restrictions  above  are enforced after .profile and the ENV files
       are interpreted.

       When a command to be executed is found to be a  shell  procedure,  rksh
       invokes ksh to execute it.  Thus, it is possible to provide to the end-
       user shell procedures that have access to the full power of  the  stan-
       dard  shell,  while  imposing  a  limited menu of commands; this scheme
       assumes that the end-user does not have write and  execute  permissions
       in the same directory.

       The  net  effect  of these rules is that the writer of the .profile has
       complete control over user  actions,  by  performing  guaranteed  setup
       actions  and leaving the user in an appropriate directory (probably not
       the login directory).

       The system administrator often sets up a directory of  commands  (e.g.,
       /usr/rbin) that can be safely invoked by rksh.

EXIT STATUS
       Errors detected by the shell, such as syntax errors, cause the shell to
       return a non-zero exit status.  If the shell is being used non-interac-
       tively,  then execution of the shell file is abandoned unless the error
       occurs inside a subshell in which case the subshell is abandoned.  Oth-
       erwise,  the shell returns the exit status of the last command executed
       (see also the exit command above).  Run time  errors  detected  by  the
       shell  are  reported  by  printing the command or function name and the
       error condition.  If the line number that  the  error  occurred  on  is
       greater than one, then the line number is also printed in square brack-
       ets ([]) after the command or function name.

FILES
       /etc/profile
              The system wide initialization file, executed for login shells.

       $HOME/.profile
              The personal initialization  file,  executed  for  login  shells
              after /etc/profile.

       $HOME/..kshrc
              Default  personal  initialization file, executed for interactive
              shells when ENV is not set.

       /etc/suid_profile
              Alternative initialization file, executed instead  of  the  per-
              sonal  initialization  file  when the real and effective user or
              group id do not match.

       /dev/null
              NULL device

SEE ALSO
       cat(1), cd(1), chmod(1), cut(1), egrep(1), echo(1),  emacs(1),  env(1),
       fgrep(1),  gmacs(1),  grep(1),  newgrp(1), pfexec(1), stty(1), test(1),
       umask(1),  vi(1),  dup(2),  exec(2),  fork(2),  getpwnam(3),  ioctl(2),
       lseek(2),   paste(1),   pathconf(2),   pipe(2),  sysconf(2),  umask(2),
       ulimit(2), wait(2), wctrans(3), rand(3),  a.out(5),  profile(5),  envi-
       ron(7).

       Morris  I. Bolsky and David G. Korn, The New KornShell Command and Pro-
       gramming Language, Prentice Hall, 1995.

       POSIX - Part 2: Shell and  Utilities,  IEEE  Std  1003.2-1992,  ISO/IEC
       9945-2, IEEE, 1993.

CAVEATS
       If  a  command  is  executed,  and then a command with the same name is
       installed in a directory in the search path before the directory  where
       the  original  command  was  found, the shell will continue to exec the
       original command.  Use the -t option of the alias  command  to  correct
       this situation.

       Some very old shell scripts contain a ^ as a synonym for the pipe char-
       acter |.

       Using the hist built-in command within a compound  command  will  cause
       the whole command to disappear from the history file.

       The  built-in  command  . file reads the whole file before any commands
       are executed.  Therefore, alias and unalias commands in the  file  will
       not apply to any commands defined in the file.

       Traps  are  not  processed  while  a  job  is  waiting for a foreground
       process.  Thus, a trap on CHLD won't be executed until  the  foreground
       job terminates.

       It  is  a good idea to leave a space after the comma operator in arith-
       metic expressions to prevent the comma from being  interpreted  as  the
       decimal point character in certain locales.



                                                                        KSH(1)