Go to main content

man pages section 1: User Commands

Exit Print View

Updated: Wednesday, August 8, 2018
 
 

sh (1)

Name

sh - standard and job control shell and command interpreter

Synopsis

/usr/bin/sh  [-acefhiknprstuvx] [argument]...


/usr/xpg4/bin/sh  [+- abCefhikmnoprstuvx]
[+- o option]... [-c string] [arg]...


/usr/bin/jsh  [-acefhiknprstuvx] [argument]...

Description

sh(1)                            User Commands                           sh(1)



NAME
       sh, jsh - standard and job control shell and command interpreter

SYNOPSIS
       /usr/bin/sh  [-acefhiknprstuvx] [argument]...


       /usr/xpg4/bin/sh  [+- abCefhikmnoprstuvx]
            [+- o option]... [-c string] [arg]...


       /usr/bin/jsh  [-acefhiknprstuvx] [argument]...


DESCRIPTION
       The /usr/bin/sh utility is a command programming language that executes
       commands read from a terminal or a file.


       The /usr/xpg4/bin/sh utility is a standards compliant shell. This util-
       ity  provides  all  the functionality of ksh88(1), except in cases dis-
       cussed in ksh88(1) where differences in behavior exist.


       The jsh utility is an interface to the shell that provides all  of  the
       functionality  of  sh  and enables job control (see Job Control section
       below).


       Arguments to the shell are listed in the Invocation section below.

   Definitions
       A blank is a tab or a space. A name is a  sequence  of  ASCII  letters,
       digits,  or  underscores,  beginning  with a letter or an underscore. A
       parameter is a name, a digit, or any of the characters *, @, #,  ?,  -,
       $, and !.

USAGE
   Commands
       A  simple-command is a sequence of non-blank words separated by blanks.
       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 if it termi-
       nates normally, or (octal) 200+status if it terminates abnormally.  See
       signal.h(3HEAD) for a list of status values.


       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 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 in
       the pipeline.


       A list is a sequence of one or more pipelines separated by ;, &, &&, or
       ||, and optionally terminated by ; or &. Of these four symbols, ; and &
       have equal precedence, which is lower than that of && and ||. The  sym-
       bols  &&  and  ||  also  have  equal precedence. A semicolon (;) causes
       sequential execution of the preceding  pipeline,  that  is,  the  shell
       waits  for the pipeline to finish before executing any commands follow-
       ing the semicolon. An ampersand (&) causes  asynchronous  execution  of
       the preceding pipeline, that is, the shell does not wait for that pipe-
       line to finish. The symbol && (||) causes the list following it  to  be
       executed  only if the preceding pipeline returns a zero (non-zero) exit
       status. An arbitrary number of newlines can appear in a  list,  instead
       of semicolons, to delimit commands.


       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 name [ in word ... ] do list done

           Each  time  a for command is executed, name 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 positional parameter
           that is set (see Parameter Substitution section  below).  Execution
           ends when there are no more words in the list.


       case word in [ pattern [ | pattern ] ) list ;; ] ...  esac

           A  case command executes the list associated with the first pattern
           that matches word. The form of the patterns is  the  same  as  that
           used  for  file-name generation (see File Name Generation section),
           except that a slash, a leading dot, or a dot immediately  following
           a slash need not be matched explicitly.



       if list ; then list elif list ; then list ; ] ... [ else list ; ] fi


       The  list  following if is executed and, if it returns a zero exit sta-
       tus, the list following the first then is executed. Otherwise, the list
       following  elif is executed and, if its value is zero, the list follow-
       ing the next then is executed. Failing that, the else list is executed.
       If no else list or then list is executed, then the if command returns a
       zero exit status.

       while 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 can be used in place of  while
                                  to negate the loop termination test.


       (list)                     Execute list in a sub-shell.


       { list;}                   list  is  executed  in the current (that is,
                                  parent) shell. The { must be followed  by  a
                                  space.


       name () { list;}           Define  a  function  which  is referenced by
                                  name. The body of the function is  the  list
                                  of  commands  between { and }. The { must be
                                  followed by a space. Execution of  functions
                                  is  described below (see Execution section).
                                  The { and } are unnecessary if the  body  of
                                  the  function is a command as defined above,
                                  under Commands.



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


       if  then  else  elif  fi  case  esac  for  while  until  do  done  {  }

   Comments Lines
       A  word beginning with # causes that word and all the following charac-
       ters up to a newline to be ignored.

   Command Substitution
       The shell reads commands from the string between two grave accents (``)
       and  the standard output from these commands can be used as all or part
       of a word. Trailing newlines from the standard output are removed.


       No interpretation is done on the string  before  the  string  is  read,
       except to remove backslashes (\) used to escape other characters. Back-
       slashes can be used to escape a grave accent (`) or  another  backslash
       (\)  and  are removed before the command string is read. Escaping grave
       accents allows nested command substitution. If the command substitution
       lies  within  a  pair of double quotes (" ...` ...` ... "), a backslash
       used to escape a double quote (\") is removed. Otherwise,  it  is  left
       intact.


       If  a  backslash is used to escape a newline character (\newline), both
       the backslash and the newline are removed (see  the  later  section  on
       Quoting). In addition, backslashes used to escape dollar signs (\$) are
       removed. Since no parameter substitution is done on the command  string
       before it is read, inserting a backslash to escape a dollar sign has no
       effect. Backslashes that precede characters other than \,  `,  ",  new-
       line, and $ are left intact when the command string is read.

   Parameter Substitution
       The  character  $  is used to introduce substitutable parameters. There
       are two types of parameters, positional and keyword. If parameter is  a
       digit,  it  is  a  positional  parameter.  Positional parameters can be
       assigned values by set. Keyword parameters (also  known  as  variables)
       can be assigned values by writing:


       name=value [ name=value ] ...


       Pattern-matching  is not performed on value. There cannot be a function
       and a variable with the same name.

       ${parameter}             The value, if any, of the parameter is substi-
                                tuted.  The  braces  are  required  only  when
                                parameter is followed by a letter,  digit,  or
                                underscore  that  is  not to be interpreted as
                                part of its name. If parameter is * or @,  all
                                the  positional  parameters, starting with $1,
                                are substituted (separated by spaces). Parame-
                                ter  $0  is  set  from  argument zero when the
                                shell is invoked.


       ${parameter:-word}       Use Default Values. If parameter is  unset  or
                                null,  the  expansion  of word is substituted;
                                otherwise, the value of parameter  is  substi-
                                tuted.


       ${parameter:=word}       Assign  Default  Values. If parameter is unset
                                or null, the expansion of word is assigned  to
                                parameter.  In  all  cases, the final value of
                                parameter is substituted. Only variables,  not
                                positional  parameters  or special parameters,
                                can be assigned in this way.


       ${parameter:?word}       If parameter is set and is  non-null,  substi-
                                tute its value; otherwise, print word and exit
                                from the shell. If word is omitted,  the  mes-
                                sage "parameter null or not set" is printed.


       ${parameter:+word}       If  parameter  is set and is non-null, substi-
                                tute word; otherwise 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:

         echo  ${d:-`pwd`}




       If the colon (:) is omitted from the above expressions, the shell  only
       checks whether parameter is set or not.


       The following parameters are automatically set by the shell.

       #       The number of positional parameters in decimal.


       -       Flags  supplied  to  the shell on invocation or by the set com-
               mand.


       ?       The decimal value returned by the last  synchronously  executed
               command.


       $       The process number of this shell.


       !       The process number of the last background command invoked.



       The  following parameters are used by the shell. The parameters in this
       section are also referred to as environment variables.

       HOME         The default argument (home directory) for the cd  command,
                    set  to  the  user's  login directory by login(1) from the
                    password file (see passwd(5)).


       PATH         The  search  path  for  commands  (see  Execution  section
                    below).


       CDPATH       The search path for the cd command.


       MAIL         If  this  parameter  is set to the name of a mail file and
                    the MAILPATH  parameter is not set, the shell informs  the
                    user of the arrival of mail in the specified file.


       MAILCHECK    This  parameter specifies how often (in seconds) the shell
                    checks for the arrival of mail in the files  specified  by
                    the  MAILPATH or MAIL parameters. The default value is 600
                    seconds (10 minutes). If set to 0, the shell checks before
                    each prompt.


       MAILPATH     A colon-separated list of file names. If this parameter is
                    set, the shell informs the user of the arrival of mail  in
                    any of the specified files. Each file name can be followed
                    by % and a message that is e printed when the modification
                    time changes. The default message is, you have mail.


       PS1          Primary prompt string, by default " $ ".


       PS2          Secondary prompt string, by default " > ".


       IFS          Internal  field  separators, normally space, tab, and new-
                    line (see Blank Interpretation section).


       SHACCT       If this parameter is set to the name of a file writable by
                    the  user,  the  shell  writes an accounting record in the
                    file for each shell procedure executed.


       SHELL        When the shell is invoked, it scans the  environment  (see
                    Environment section below) for this name.



       See  environ(7) for descriptions of the following environment variables
       that affect the execution of sh: LC_CTYPE and LC_MESSAGES.


       The shell gives default values to PATH, PS1, PS2, MAILCHECK,  and  IFS.
       Default values for HOME and MAIL are set by login(1).

   Blank Interpretation
       After  parameter  and command substitution, the results of substitution
       are scanned for internal field separator  characters  (those  found  in
       IFS) and split into distinct arguments where such characters are found.
       Explicit null arguments ("" or '') are retained.  Implicit  null  argu-
       ments  (those  resulting  from  parameters  that  have  no  values) are
       removed.

   Input/Output Redirection
       A command's input and output can be redirected using a special notation
       interpreted  by  the shell. The following can appear anywhere in a sim-
       ple-command or can precede or follow a command and are not passed on as
       arguments to the invoked command. Note: Parameter and command substitu-
       tion occurs before word or digit is used.

       <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, it is created; otherwise,
                       it is truncated to zero length.


       >>word          Use file word as standard output. If the  file  exists,
                       output  is  appended to it by first seeking to the EOF.
                       Otherwise, the file is created.


       <>word          Open file word for  reading  and  writing  as  standard
                       input.


       <<[-]word       After  parameter  and  command  substitution is done on
                       word, the shell input is read up to the first line that
                       literally matches the resulting word, or to an EOF. If,
                       however, the hyphen (-) is appended to <<:

                           1.     leading tabs are stripped from  word  before
                                  the shell input is read (but after parameter
                                  and command substitution is done on word);

                           2.     leading tabs are  stripped  from  the  shell
                                  input  as it is read and before each line is
                                  compared with word; and

                           3.     shell input is read up  to  the  first  line
                                  that  literally  matches the resulting word,
                                  or to an EOF.
                       If any character of word is quoted (see Quoting section
                       later),  no  additional processing is done to the shell
                       input. If no characters of word are quoted:

                           1.     parameter and command substitution occurs;

                           2.     (escaped) \newlines are removed; and

                           3.     \ must be used to quote the characters \, $,
                                  and `.
                       The resulting document becomes the standard input.


       <&digit         Use  the  file associated with file descriptor digit as
                       standard input. Similarly for the standard output using
                       >&digit.


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



       If any of the above is preceded by a digit, the file  descriptor  which
       is  associated with the file is that specified by the digit (instead of
       the default 0 or 1). For example:

         ... 2>&1




       associates file descriptor 2 with the file  currently  associated  with
       file descriptor 1.


       The order in which redirections are specified is significant. The shell
       evaluates redirections left-to-right. For example:

         ... 1>xxx 2>&1




       first associates file descriptor 1 with file xxx.  It  associates  file
       descriptor  2 with the file associated with file descriptor 1 (that is,
       xxx). If the order of redirections were  reversed,  file  descriptor  2
       would  be  associated with the terminal (assuming file descriptor 1 had
       been) and file descriptor 1 would be associated with file xxx.


       Using the terminology introduced on the first page, under Commands,  if
       a command is composed of several simple commands, redirection is evalu-
       ated for the entire command before it is evaluated for each simple com-
       mand.  That  is,  the  shell evaluates redirection for the entire list,
       then each pipeline within the list, then each command within each pipe-
       line, then each list within each command.


       If  a command is followed by &, the default standard input for the com-
       mand 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.

   File Name Generation
       Before a command is executed, each command  word  is  scanned  for  the
       characters  *, ?, and [. If one of these characters appears the word is
       regarded as a pattern. The word is replaced with alphabetically  sorted
       file  names  that  match  the  pattern.  If  no file name is found that
       matches the pattern, the word is left unchanged. The character . at the
       start of a file name or immediately following a /, as well as the char-
       acter / itself, must be matched explicitly.

       *            Matches any string, including the null string.


       ?            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 !, any character not enclosed is
                    matched.



       Notice that all quoted characters (see below) must be  matched  explic-
       itly in a filename.

   Quoting
       The  following characters have a special meaning to the shell and cause
       termination of a word unless quoted:


       ;  &  (  )  |  ^  <  >  newline  space  tab


       A character can be quoted (that is, made to stand for itself)  by  pre-
       ceding  it with a backslash (\) or inserting it between a pair of quote
       marks ('' or ""). During processing, the shell can quote certain  char-
       acters  to  prevent  them from taking on a special meaning. Backslashes
       used to quote a single character are removed from the word  before  the
       command  is  executed.  The pair \newline is removed from a word before
       command and parameter substitution.


       All characters enclosed between a pair  of  single  quote  marks  (''),
       except  a  single quote, are quoted by the shell. Backslash has no spe-
       cial meaning inside a pair of single quotes.  A  single  quote  can  be
       quoted  inside  a  pair of double quote marks (for example, "'"), but a
       single quote can not be quoted inside a pair of single quotes.


       Inside a pair of double quote marks (""), parameter and command substi-
       tution occurs and the shell quotes the results to avoid blank interpre-
       tation and file name generation. If $*  is  within  a  pair  of  double
       quotes, the positional parameters are substituted and quoted, separated
       by quoted spaces ("$1 $2 ..."). However, if $@ is within a pair of dou-
       ble quotes, the positional parameters are substituted and quoted, sepa-
       rated by unquoted spaces ("$1""$2"  ... ). \ quotes the  characters  \,
       `,  , (comma), and $. The pair \newline is removed before parameter and
       command substitution. If a backslash precedes characters other than  \,
       `,  ,  (comma),  $, and newline, then the backslash itself is quoted by
       the shell.

   Prompting
       When used interactively, the shell prompts with the value of PS1 before
       reading  a command. If at any time a newline is typed and further input
       is needed to complete a command, the secondary  prompt  (that  is,  the
       value of PS2) is issued.

   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  shell  interacts  with  the environment in several ways. On
       invocation, the shell scans the environment and creates a parameter for
       each  name  found, giving it the corresponding value. If the user modi-
       fies the value of any of these parameters or  creates  new  parameters,
       none of these affects the environment unless the export command is used
       to bind the shell's parameter to the environment (see also set  -a).  A
       parameter  can  be removed from the environment with the unset command.
       The environment seen by any executed command is thus  composed  of  any
       unmodified  name-value  pairs  originally inherited by the shell, minus
       any pairs removed by unset, plus any modifications or additions, all of
       which must be noted in export commands.


       The environment for any simple-command can be augmented by prefixing it
       with one or more assignments to parameters. Thus:

         TERM=450  command




       and

         (export TERM; TERM=450;   command




       are equivalent as far as the execution of command is concerned if  com-
       mand is not a Special Command. If command is a Special Command, then

         TERM=450   command




       modifies the TERM variable in the current shell.


       If the -k flag is set, all keyword arguments are placed in the environ-
       ment, even if they occur after the command name. The following  example
       first prints a=b c and c:

         echo a=b  c

         a=b  c

         set  -k

         echo a=b  c

         c



   Signals
       The  INTERRUPT  and  QUIT signals for an invoked command are ignored if
       the command is followed by &. Otherwise, signals have the values inher-
       ited by the shell from its parent, with the exception of signal 11 (but
       see also the trap command below).

   Execution
       Each time a command is executed, the  command  substitution,  parameter
       substitution, blank interpretation, input/output redirection, and file-
       name generation listed above are  carried  out.  If  the  command  name
       matches the name of a defined function, the function is executed in the
       shell process (note how this differs from the execution of shell script
       files,  which  require a sub-shell for invocation). If the command name
       does not match the name of a defined function, but matches one  of  the
       Special Commands listed below, it is executed in the shell process.


       The  positional  parameters $1, $2, ... are set to the arguments of the
       function. If the command name matches neither a Special Command nor the
       name  of a defined function, a new process is created and an attempt is
       made to execute the command via exec(2).


       The shell parameter PATH defines the search path for the directory con-
       taining  the  command.  Alternative  directory names are separated by a
       colon (:). The default path is /usr/bin. The current directory is spec-
       ified by a null path name, which can appear immediately after the equal
       sign, between two colon delimiters anywhere in the path list, or at the
       end  of the path list. If the command name contains a / the search path
       is not used. Otherwise, each directory in the path is searched  for  an
       executable file. If the file has execute permission but is not an a.out
       file, it is assumed to be a file containing shell commands. A sub-shell
       is  spawned  to  read it. A parenthesized command is also executed in a
       sub-shell.


       The location in the search path where a command was found is remembered
       by  the  shell  (to help avoid unnecessary execs later). If the command
       was found in a relative directory, its location must  be  re-determined
       whenever  the  current  directory changes. The shell forgets all remem-
       bered locations whenever the PATH variable is changed or  the  hash  -r
       command is executed (see below).

   Special Commands
       Input/output  redirection  is  now  permitted  for these commands. File
       descriptor 1 is the  default  output  location.  When  Job  Control  is
       enabled,  additional Special Commands are added to the shell's environ-
       ment (see Job Control section below).

       :

           No effect; the command does nothing. A zero exit code is returned.


       . filename

           Read and execute commands from filename and return. The search path
           specified  by  PATH  is used to find the directory containing file-
           name.


       bg [%jobid ...]

           When Job Control is enabled, the bg command is added to the  user's
           environment  to manipulate jobs. Resumes the execution of a stopped
           job in the background. If %jobid is  omitted  the  current  job  is
           assumed. (See Job Control section below for more detail.)


       break [ n ]

           Exit  from  the enclosing for or while loop, if any. If n is speci-
           fied, break n levels.


       cd [ argument ]

           Change the current directory to argument. The shell parameter  HOME
           is  the  default  argument.  The shell parameter CDPATH defines the
           search path for  the  directory  containing  argument.  Alternative
           directory  names  are separated by a colon (:). The default path is
           <null> (specifying the current directory). Note: The current direc-
           tory 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 argument begins with a / the search path is
           not used. Otherwise, each directory in the  path  is  searched  for
           argument.


       chdir [ dir ]

           chdir changes the shell's working directory to directory dir. If no
           argument is given, change to the home directory of the user. If dir
           is  a  relative  pathname not found in the current directory, check
           for it in those directories listed in the CDPATH variable.  If  dir
           is the name of a shell variable whose value starts with a /, change
           to the directory named by that value.


       continue [ n ]

           Resume the next iteration of the enclosing for or while loop. If  n
           is specified, resume at the n-th enclosing loop.


       echo [ arguments ... ]

           The  words in arguments are written to the shell's standard output,
           separated by space characters. See echo(1)  for  fuller  usage  and
           description.


       eval [ argument ... ]

           The arguments are read as input to the shell and the resulting com-
           mand(s) executed.


       exec [ argument ... ]

           The command specified by the arguments is executed in place of this
           shell  without  creating  a new process. Input/output arguments can
           appear and, if no  other  arguments  are  given,  cause  the  shell
           input/output to be modified.


       exit [ n ]

           Causes the calling shell or shell script to exit with the exit sta-
           tus specified by n. If n is omitted the exit status is that of  the
           last command executed (an EOF also causes the shell to exit.)


       export [ name ... ]

           The  given names are marked for automatic export to the environment
           of subsequently executed commands. If no arguments are given, vari-
           able  names  that  have  been  marked for export during the current
           shell's execution are listed. (Variable names exported from a  par-
           ent  shell  are listed only if they have been exported again during
           the current shell's execution.) Function names are not exported.


       fg [%jobid ...]

           When Job Control is enabled, the fg command is added to the  user's
           environment  to manipulate jobs. This command resumes the execution
           of a stopped job in the foreground  and  also  moves  an  executing
           background  job into the foreground. If %jobid is omitted, the cur-
           rent job is assumed.  (See  Job  Control  section  below  for  more
           detail.)


       getopts

           Use  in  shell  scripts  to  support  command syntax standards (see
           Intro(1)). This command parses positional parameters and checks for
           legal options. See getoptcvt(1) for usage and description.


       hash [ -r ] [ name ... ]

           For each name, the location in the search path of the command spec-
           ified by name is determined and remembered by  the  shell.  The  -r
           option  causes  the shell to forget all remembered locations. If no
           arguments are given, information about remembered commands is  pre-
           sented.  Hits  is the number of times a command has been invoked by
           the shell process. Cost is a measure of the work required to locate
           a command in the search path. If a command is found in a "relative"
           directory in the search path, after changing to that directory, the
           stored location of that command is recalculated. Commands for which
           this are done are indicated by an asterisk (*) adjacent to the hits
           information. Cost is incremented when the recalculation is done.


       jobs [-p|-l] [%jobid ...]
       jobs -x command [arguments]

           Reports  all  jobs that are stopped or executing in the background.
           If %jobid is omitted, all jobs that are stopped or running  in  the
           background  are  reported.  (See Job Control section below for more
           detail.)


       kill [ -sig ] %job ...
       kill -l

           Sends either the TERM (terminate) signal or the specified signal to
           the specified jobs or processes. Signals are either given by number
           or by names (as given in signal.h(3HEAD)  stripped  of  the  prefix
           "SIG"  with the exception that SIGCHD is named CHLD). If the signal
           being sent is TERM (terminate) or HUP (hangup),  then  the  job  or
           process  is  sent  a  CONT  (continue) signal if it is stopped. The
           argument job can be the process id of a process that is not a  mem-
           ber  of one of the active jobs. See Job Control section below for a
           description of the format of job. In the second form, kill -l,  the
           signal numbers and names are listed. (See kill(1)).


       login [ argument ... ]

           Equivalent  to `exec login argument....' See login(1) for usage and
           description.


       newgrp [ argument ]

           Equivalent to exec newgrp argument. See  newgrp(1)  for  usage  and
           description.


       pwd

           Print  the  current  working  directory.  See  pwd(1) for usage and
           description.


       read name ...

           One line is read from the standard input and,  using  the  internal
           field  separator,  IFS  (normally  space  or  tab), to delimit word
           boundaries, the first word is assigned to the first name, the  sec-
           ond  word  to  the  second  name, and so forth, with leftover words
           assigned to the last name. Lines can be continued  using  \newline.
           Characters  other than newline can be quoted by preceding them with
           a  backslash.  These  backslashes  are  removed  before  words  are
           assigned  to  names, and no interpretation is done on the character
           that follows the backslash. The return code is 0, unless an EOF  is
           encountered.


       readonly [ name ... ]

           The  given  names  are  marked readonly and the values of the these
           names can not be changed by subsequent assignment. If no  arguments
           are given, a list of all readonly names is printed.


       return [ n ]

           Causes  a function to exit with the return value specified by n. If
           n is omitted, the return status is that of the  last  command  exe-
           cuted.


       set [ -aefhkntuvx [ argument ... ] ]


           -a    Mark variables which are modified or created for export.


           -e    Exit immediately if a command exits with a non-zero exit sta-
                 tus.


           -f    Disable file name generation.


           -h    Locate  and  remember  function  commands  as  functions  are
                 defined  (function  commands  are  normally  located when the
                 function is executed).


           -k    All keyword arguments are placed in  the  environment  for  a
                 command, not just those that precede the command name.


           -n    Read commands but do not execute them.


           -t    Exit after reading and executing one command.


           -u    Treat unset variables 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 flags; useful in setting $1 to -.

           Using  +  rather  than - causes these flags to be turned off. These
           flags can also be used upon invocation of the  shell.  The  current
           set  of flags can be found in $-. The remaining arguments are posi-
           tional parameters and are assigned, in order, to $1, $2, ... If  no
           arguments are given, the values of all names are printed.


       shift [ n ]

           The  positional  parameters from $n+1 ... are renamed $1 ... . If n
           is not given, it is assumed to be 1.


       stop pid ...

           Halt execution of the process number pid. (see ps(1)).


       suspend

           Stops the execution of the current shell (but  not  if  it  is  the
           login shell).


       test

           Evaluate   conditional  expressions.  See  test(1)  for  usage  and
           description.


       times

           Print the accumulated user and system times for processes run  from
           the shell.


       trap [ argument n [ n2 ... ]]

           The  command  argument  is  to  be read and executed when the shell
           receives numeric or symbolic  signal(s)  (n).  (Note:  argument  is
           scanned once when the trap is set and once when the trap is taken.)
           Trap commands are executed in order of signal number or correspond-
           ing  symbolic names. Any attempt to set a trap on a signal that was
           ignored on entry to the current shell is ineffective. An attempt to
           trap  on signal 11 (memory fault) produces an error. If argument is
           absent, all trap(s) n are reset to their original values. If  argu-
           ment is the null string, this signal is ignored by the shell and by
           the commands it invokes. If n is 0, the command  argument  is  exe-
           cuted  on  exit  from the shell. The trap command with no arguments
           prints a list of commands associated with each signal number.


       type [ name ... ]

           For each name, indicate how it would be interpreted if  used  as  a
           command name.


       ulimit [ [-HS] [-a | -cdfnstv] ]
       ulimit [ [-HS] [-c | -d | -f | -n | -s | -t | -v] ] limit

           ulimit  prints  or  sets hard or soft resource limits. These limits
           are described in getrlimit(2).

           If limit is not present, ulimit prints the  specified  limits.  Any
           number  of  limits can be printed at one time. The -a option prints
           all limits.

           If limit is present, ulimit sets the specified limit to limit.  The
           string  unlimited  requests  that  the  current  limit,  if any, be
           removed. Any user can set a soft limit  to any value less  than  or
           equal  to  the hard limit. Any user can lower a hard limit.  Only a
           user with appropriate privileges can raise or remove a hard  limit.
           See getrlimit(2).

           The  -H  option  specifies  a hard limit. The -S option specifies a
           soft limit. If neither option is specified, ulimit sets both limits
           and print the soft limit.

           The  following  options specify the resource whose limits are to be
           printed or set. If no option is specified, the file size  limit  is
           printed or set.

           -c    maximum core file size (in 512-byte blocks)


           -d    maximum size of data segment or heap (in kbytes)


           -f    maximum file size (in 512-byte blocks)


           -n    maximum file descriptor plus 1


           -s    maximum size of stack segment (in kbytes)


           -t    maximum CPU time (in seconds)


           -v    maximum size of virtual memory (in kbytes)

           Run the sysdef(8) command to obtain the maximum possible limits for
           your system. The values reported are in  hexadecimal,  but  can  be
           translated  into  decimal  numbers  using  the  bc(1)  utility. See
           swap(8).)

           As an example of ulimit, to limit the size of a core file dump to 0
           Megabytes, type the following:

             ulimit -c 0




       umask [ nnn ]

           The user file-creation mask is set to nnn (see umask(1)). If nnn is
           omitted, the current value of the mask is printed.


       unset [ name ... ]

           For each name, remove the corresponding variable or function value.
           The variables PATH, PS1, PS2, MAILCHECK, and IFS cannot be unset.


       wait [ n ]

           Wait  for  your background process whose process id is n and report
           its termination status. If n is omitted, all your shell's currently
           active  background  processes are waited for and the return code is
           zero.


   Invocation
       If the shell is invoked through exec(2)  and  the  first  character  of
       argument  zero  is -, commands are initially read from /etc/profile and
       from $HOME/.profile, if such files exist. Thereafter, commands are read
       as described below, which is also the case when the shell is invoked as
       /usr/bin/sh. The flags below are interpreted by the shell on invocation
       only.  Note:  Unless the -c or -s flag is specified, the first argument
       is assumed to be the name  of  a  file  containing  commands,  and  the
       remaining arguments are passed as positional parameters to that command
       file:

       -c string      If the -c flag is present commands are read from string.


       -i             If the -i flag is present or if the shell input and out-
                      put  are  attached to a terminal, this shell is interac-
                      tive. In this case, TERMINATE is ignored (so that kill 0
                      does  not  kill  an  interactive shell) and INTERRUPT is
                      caught and ignored (so that wait is  interruptible).  In
                      all cases, QUIT is ignored by the shell.


       -p             If  the  -p  flag is present, the shell does not set the
                      effective user and group IDs to the real user and  group
                      IDs.


       -r             If  the  -r  flag  is  present the shell is a restricted
                      shell (see rsh(8)).


       -s             If the -s flag is present or  if  no  arguments  remain,
                      commands are read from the standard input. Any remaining
                      arguments specify the positional parameters. Shell  out-
                      put  (except  for  Special  Commands) is written to file
                      descriptor 2.



       The remaining flags and arguments are described under the  set  command
       above.

   Job Control (jsh)
       When the shell is invoked as jsh, Job Control is enabled in addition to
       all of the functionality described previously for  sh.  Typically,  Job
       Control  is  enabled  for  the  interactive shell only. Non-interactive
       shells typically do not benefit from the  added  functionality  of  Job
       Control.


       With  Job Control enabled, every command or pipeline the user enters at
       the terminal is called a job. All jobs exist in one  of  the  following
       states:  foreground, background, or stopped. These terms are defined as
       follows:

           1.     A job in the foreground has read and  write  access  to  the
                  controlling terminal.

           2.     A job in the background is denied read access and has condi-
                  tional  write  access  to  the  controlling  terminal   (see
                  stty(1)).

           3.     A  stopped  job is a job that has been placed in a suspended
                  state, usually as a result of a  SIGTSTP  signal  (see  sig-
                  nal.h(3HEAD)).


       Every  job that the shell starts is assigned a positive integer, called
       a job number which is tracked by the shell and is used as an identifier
       to  indicate a specific job. Additionally, the shell keeps track of the
       current and previous jobs. The current job is the most recent job to be
       started or restarted. The previous job is the first non-current job.


       The acceptable syntax for a Job Identifier is of the form:


       %jobid


       where jobid can be specified in any of the following formats:

       % or +       For the current job.


       -            For the previous job.


       ?<string>    Specify  the  job for which the command line uniquely con-
                    tains string.


       n            For job number n.


       pref         Where pref is a unique prefix of  the  command  name.  For
                    example,  if  the  command  ls -l name were running in the
                    background, it could be referred to as  %ls.  pref  cannot
                    contain blanks unless it is quoted.



       When  Job  Control  is enabled, the following commands are added to the
       user's environment to manipulate jobs:

       bg [%jobid ...]

           Resumes the execution of a stopped job in the background. If %jobid
           is omitted the current job is assumed.


       fg [%jobid ...]

           Resumes  the  execution  of  a  stopped job in the foreground, also
           moves an executing background job into the foreground. If %jobid is
           omitted the current job is assumed.


       jobs [-p|-l] [%jobid ...]
       jobs -x command [arguments]

           Reports  all  jobs that are stopped or executing in the background.
           If %jobid is omitted, all jobs that are stopped or running  in  the
           background  is  reported.  The following options modify/enhance the
           output of jobs:

           -l    Report the process group ID  and  working  directory  of  the
                 jobs.


           -p    Report only the process group ID of the jobs.


           -x    Replace any jobid found in command or arguments with the cor-
                 responding process group ID, and then execute command passing
                 it arguments.



       kill [ -signal ] %jobid

           Builtin  version  of  kill to provide the functionality of the kill
           command for processes identified with a jobid.


       stop %jobid ...

           Stops the execution of a background job(s).


       suspend

           Stops the execution of the current shell (but  not  if  it  is  the
           login shell).


       wait [%jobid ...]

           wait  builtin  accepts  a job identifier. If %jobid is omitted wait
           behaves as described above under Special Commands.


   Large File Behavior
       See lfcompile(7) for the description of the behavior of sh and jsh when
       encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).

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  execution  of the shell file is abandoned. Otherwise, the shell
       returns the exit status of the last command executed (see also the exit
       command above).

   jsh Only
       If the shell is invoked as jsh and an attempt is made to exit the shell
       while there are stopped jobs, the shell issues one warning:


       There are stopped jobs.


       This is the only message. If another exit attempt is  made,  and  there
       are  still  stopped  jobs they are sent a SIGHUP signal from the kernel
       and the shell is exited.

FILES
       $HOME/.profile


       /dev/null


       /etc/profile


       /tmp/sh*

ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:

   /usr/bin/sh, /usr/bin/jsh
       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE         |      ATTRIBUTE VALUE        |
       +-----------------------------+-----------------------------+
       |Availability                 |system/core-os               |
       +-----------------------------+-----------------------------+
       |CSI                          |Enabled                      |
       +-----------------------------+-----------------------------+

   /usr/xpg4/bin/sh
       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE         |      ATTRIBUTE VALUE        |
       +-----------------------------+-----------------------------+
       |Availability                 |system/core-os               |
       +-----------------------------+-----------------------------+
       |CSI                          |Enabled                      |
       +-----------------------------+-----------------------------+

SEE ALSO
       Intro(1), bc(1), echo(1), getoptcvt(1),  kill(1),  ksh88(1),  login(1),
       newgrp(1),     pfsh(1),     pfexec(1),     ps(1),    pwd(1),    set(1),
       shell_builtins(1), stty(1), test(1), umask(1), wait(1), rsh(8),  su(8),
       swap(8),  sysdef(8),  dup(2),  exec(2), fork(2), getrlimit(2), pipe(2),
       ulimit(2),  setlocale(3C),  signal.h(3HEAD),   passwd(5),   profile(5),
       attributes(7), environ(7), lfcompile(7), XPG4(7)

WARNINGS
       The use of setuid shell scripts is strongly discouraged.

NOTES
       Words  used  for  filenames  in input/output redirection are not inter-
       preted for  filename  generation  (see  File  Name  Generation  section
       above). For example, cat file1 >a* createsa file named a*.


       Because  commands in pipelines are run as separate processes, variables
       set in a pipeline have no effect on the parent shell.


       If the input or the output of a while or until loop is redirected,  the
       commands  in  the  loop  are  run  in a sub-shell, and variables set or
       changed there have no effect on the parent process:

            lastline=
            while read line
            do

                    lastline=$line
            done < /etc/passwd
            echo "lastline=$lastline"       # lastline is empty!




       In these cases, the input or output can be redirected by using exec, as
       in the following example:

            # Save standard input (file descriptor 0) as file
            # descriptor 3, and redirect standard input from the file
            /etc/passwd:

            exec 3<&0               # save standard input as fd 3
            exec </etc/passwd       # redirect input from file

            lastline=
            while read line
            do
                    lastline=$line
            done

            exec 0<&3               # restore standard input
            exec 3<&-               # close file descriptor 3
            echo "$lastline"        # lastline




       If  you  get  the error message, "cannot fork, too many processes", try
       using the wait(1) command to clean up  your  background  processes.  If
       this  doesn't  help,  the  system process table is probably full or you
       have too many active foreground processes. There is a limit to the num-
       ber  of  process  ids associated with your login, and to the number the
       system can keep track of.


       Only the last process in a pipeline can be waited for.


       If a command is executed, and a command with the same name is installed
       in a directory in the search path before the directory where the origi-
       nal command was found, the shell continues to exec  the  original  com-
       mand. Use the hash command to correct this situation.


       The  Bourne  shell has a limitation on the effective UID for a process.
       If this UID is less than 100 (and not equal to  the  real  UID  of  the
       process), then the UID is reset to the real UID of the process.


       Because the shell implements both foreground and background jobs in the
       same process group, they all receive the same signals, which  can  lead
       to  unexpected  behavior.  It is, therefore, recommended that other job
       control shells be used, especially in an interactive environment.


       When the shell executes a shell script that attempts to execute a  non-
       existent command interpreter, the shell returns an erroneous diagnostic
       message that the shell script file does not exist.



Solaris 11.4                      12 Jul 2011                            sh(1)