Go to main content

man pages section 1: User Commands

Exit Print View

Updated: Thursday, June 13, 2019

awk (1g)


awk - pattern scanning and processing language


gawk [ POSIX or GNU style options ] -f program-file [ -- ] file ...
gawk [ POSIX or GNU style options ] [ -- ] program-text file ...


GAWK(1)                        Utility Commands                        GAWK(1)

       gawk - pattern scanning and processing language

       gawk [ POSIX or GNU style options ] -f program-file [ -- ] file ...
       gawk [ POSIX or GNU style options ] [ -- ] program-text file ...

       Gawk  is  the  GNU Project's implementation of the AWK programming lan-
       guage.  It conforms to the definition of  the  language  in  the  POSIX
       1003.1  standard.   This version in turn is based on the description in
       The AWK Programming Language, by Aho, Kernighan, and Weinberger.   Gawk
       provides  the additional features found in the current version of Brian
       Kernighan's awk and numerous GNU-specific extensions.

       The command line consists of options to gawk itself,  the  AWK  program
       text  (if not supplied via the -f or -i options), and values to be made
       available in the ARGC and ARGV pre-defined AWK variables.

       When gawk is invoked with the --profile  option,  it  starts  gathering
       profiling statistics from the execution of the program.  Gawk runs more
       slowly in this mode, and automatically produces an execution profile in
       the file awkprof.out when done.  See the --profile option, below.

       Gawk  also has an integrated debugger. An interactive debugging session
       can be started by supplying the --debug option to the command line.  In
       this mode of execution, gawk loads the AWK source code and then prompts
       for debugging commands.  Gawk can only debug AWK  program  source  pro-
       vided  with  the -f option.  The debugger is documented in GAWK: Effec-
       tive AWK Programming.

       Gawk options may be either traditional POSIX-style one letter  options,
       or  GNU-style  long  options.   POSIX  options start with a single "-",
       while long options start with "--".  Long options are provided for both
       GNU-specific features and for POSIX-mandated features.

       Gawk-specific  options  are  typically used in long-option form.  Argu-
       ments to long options are either joined with the option by an  =  sign,
       with no intervening spaces, or they may be provided in the next command
       line argument.  Long options may be abbreviated, as long as the  abbre-
       viation remains unique.

       Additionally,  every  long  option has a corresponding short option, so
       that the option's functionality may be used from within #!   executable

       Gawk accepts the following options.  Standard options are listed first,
       followed by options for gawk extensions, listed alphabetically by short

       -f program-file
       --file program-file
              Read  the AWK program source from the file program-file, instead
              of from the  first  command  line  argument.   Multiple  -f  (or
              --file) options may be used.

       -F fs
       --field-separator fs
              Use fs for the input field separator (the value of the FS prede-
              fined variable).

       -v var=val
       --assign var=val
              Assign the value val to the variable var,  before  execution  of
              the  program  begins.  Such variable values are available to the
              BEGIN rule of an AWK program.

              Treat all input data as single-byte characters. In other  words,
              don't  pay any attention to the locale information when attempt-
              ing to process strings as  multibyte  characters.   The  --posix
              option overrides this one.

              Run  in compatibility mode.  In compatibility mode, gawk behaves
              identically to Brian Kernighan's awk; none of  the  GNU-specific
              extensions  are recognized.  See GNU EXTENSIONS, below, for more

              Print the short version of the GNU copyright information message
              on the standard output and exit successfully.

              Print  a  sorted list of global variables, their types and final
              values to file.  If no file is provided, gawk uses a file  named
              awkvars.out in the current directory.
              Having  a list of all the global variables is a good way to look
              for typographical errors in your programs.  You would  also  use
              this option if you have a large program with a lot of functions,
              and you want to be sure that your functions don't  inadvertently
              use  global  variables  that  you meant to be local.  (This is a
              particularly easy mistake to make  with  simple  variable  names
              like i, j, and so on.)

              Enable  debugging  of  AWK  programs.   By default, the debugger
              reads commands interactively from the keyboard (standard input).
              The  optional file argument specifies a file with a list of com-
              mands for the debugger to execute non-interactively.

       -e program-text
       --source program-text
              Use program-text as AWK program source code.  This option allows
              the  easy  intermixing of library functions (used via the -f and
              -i options) with source code entered on the command line.  It is
              intended  primarily  for  medium  to  large AWK programs used in
              shell scripts.

       -E file
       --exec file
              Similar to -f, however, this is option  is  the  last  one  pro-
              cessed.   This should be used with #!  scripts, particularly for
              CGI applications, to avoid passing in options or source code (!)
              on  the  command line from a URL.  This option disables command-
              line variable assignments.

              Scan and parse the AWK program, and generate a GNU .pot  (Porta-
              ble Object Template) format file on standard output with entries
              for all localizable strings in the program.  The program  itself
              is  not  executed.   See  the  GNU gettext distribution for more
              information on .pot files.

       --help Print a relatively short summary of the available options on the
              standard  output.   (Per the GNU Coding Standards, these options
              cause an immediate, successful exit.)

       -i include-file
       --include include-file
              Load an awk source library.  This searches for the library using
              the  AWKPATH environment variable.  If the initial search fails,
              another attempt will be made after appending  the  .awk  suffix.
              The  file  will be loaded only once (i.e., duplicates are elimi-
              nated), and the  code  does  not  constitute  the  main  program

       -l lib
       --load lib
              Load  a  gawk  extension  from  the  shared  library  lib.  This
              searches for the library using the AWKLIBPATH environment  vari-
              able.  If the initial search fails, another attempt will be made
              after appending the default shared library suffix for the  plat-
              form.   The  library  initialization  routine  is expected to be
              named dl_load().

       -L [value]
              Provide warnings about constructs that are dubious or non-porta-
              ble  to other AWK implementations.  With an optional argument of
              fatal, lint warnings become fatal errors.  This may be  drastic,
              but  its use will certainly encourage the development of cleaner
              AWK programs.  With an optional argument of invalid, only  warn-
              ings about things that are actually invalid are issued. (This is
              not fully implemented yet.)

              Force arbitrary precision arithmetic on numbers. This option has
              no  effect  if  gawk  is not compiled to use the GNU MPFR and MP
              libraries.  (In such a case, gawk issues a warning.)

              Recognize octal and hexadecimal values in input data.  Use  this
              option with great caution!

              Force  gawk  to  use  the  locale's decimal point character when
              parsing input data.  Although the POSIX standard  requires  this
              behavior,  and  gawk  does  so  when  --posix  is in effect, the
              default is to follow traditional behavior and use  a  period  as
              the  decimal  point, even in locales where the period is not the
              decimal point character.   This  option  overrides  the  default
              behavior,  without  the full draconian strictness of the --posix

              Output a pretty printed version of the program to file.   If  no
              file is provided, gawk uses a file named awkprof.out in the cur-
              rent directory.  Implies --no-optimize.

              Enable gawk's default optimizations upon the internal  represen-
              tation  of  the  program.   Currently, this includes simple con-
              stant-folding, and tail call  elimination  for  recursive  func-
              tions.  This option is on by default.

              Start  a profiling session, and send the profiling data to prof-
              file.  The default is awkprof.out.  The profile contains  execu-
              tion  counts of each statement in the program in the left margin
              and  function  call  counts  for  each  user-defined   function.
              Implies --no-optimize.

              This  turns on compatibility mode, with the following additional

              o \x escape sequences are not recognized.

              o You cannot continue lines after ?  and :.

              o The synonym func for the keyword function is not recognized.

              o The operators ** and **= cannot be used in place of ^ and ^=.

              Enable the use of interval  expressions  in  regular  expression
              matching (see Regular Expressions, below).  Interval expressions
              were not traditionally available in the AWK language.  The POSIX
              standard  added them, to make awk and egrep consistent with each
              other.  They are enabled by default, but this option remains for
              use with --traditional.

              Disable gawk's default optimizations upon the internal represen-
              tation of the program.

              Run gawk in sandbox mode, disabling the system() function, input
              redirection  with  getline,  output  redirection  with print and
              printf,  and  loading  dynamic  extensions.   Command  execution
              (through pipelines) is also disabled.  This effectively blocks a
              script from accessing local  resources,  except  for  the  files
              specified on the command line.

              Provide  warnings  about constructs that are not portable to the
              original version of UNIX awk.

              Print version information for this particular copy  of  gawk  on
              the  standard  output.  This is useful mainly for knowing if the
              current copy of gawk on your system is up to date  with  respect
              to  whatever the Free Software Foundation is distributing.  This
              is also useful when reporting bugs.  (Per the GNU  Coding  Stan-
              dards, these options cause an immediate, successful exit.)

       --     Signal the end of options. This is useful to allow further argu-
              ments to the AWK program itself to start with a "-".  This  pro-
              vides  consistency  with the argument parsing convention used by
              most other POSIX programs.

       In compatibility mode, any other options are flagged  as  invalid,  but
       are  otherwise  ignored.   In normal operation, as long as program text
       has been supplied, unknown options are passed on to the AWK program  in
       the ARGV array for processing.  This is particularly useful for running
       AWK programs via the #!  executable interpreter mechanism.

       For POSIX compatibility, the -W option may be  used,  followed  by  the
       name of a long option.

       An  AWK program consists of a sequence of optional directives, pattern-
       action statements, and optional function definitions.

              @include "filename"
              @load "filename"
              pattern   { action statements }
              function name(parameter list) { statements }

       Gawk first reads the program source from the program-file(s) if  speci-
       fied, from arguments to --source, or from the first non-option argument
       on the command line.  The -f and --source options may be used  multiple
       times  on  the command line.  Gawk reads the program text as if all the
       program-files and command  line  source  texts  had  been  concatenated
       together.   This  is  useful  for  building libraries of AWK functions,
       without having to include them in each new AWK program that uses  them.
       It also provides the ability to mix library functions with command line

       In addition, lines beginning with @include may be used to include other
       source  files  into your program, making library use even easier.  This
       is equivalent to using the -i option.

       Lines beginning with @load may be used to load extension functions into
       your program.  This is equivalent to using the -l option.

       The  environment  variable  AWKPATH specifies a search path to use when
       finding source files named with the -f and -i options.  If  this  vari-
       able  does  not  exist,  the  default path is ".:/usr/local/share/awk".
       (The actual directory may vary, depending upon how gawk was  built  and
       installed.)  If a file name given to the -f option contains a "/" char-
       acter, no path search is performed.

       The environment variable AWKLIBPATH specifies a search path to use when
       finding  source  files named with the -l option.  If this variable does
       not exist, the default  path  is  "/usr/local/lib/gawk".   (The  actual
       directory may vary, depending upon how gawk was built and installed.)

       Gawk executes AWK programs in the following order.  First, all variable
       assignments specified via the -v option are performed.  Next, gawk com-
       piles  the program into an internal form.  Then, gawk executes the code
       in the BEGIN rule(s) (if any), and then  proceeds  to  read  each  file
       named  in  the  ARGV array (up to ARGV[ARGC-1]).  If there are no files
       named on the command line, gawk reads the standard input.

       If a filename on the command line has the form var=val it is treated as
       a  variable  assignment.   The  variable var will be assigned the value
       val.  (This happens after any BEGIN rule(s) have  been  run.)   Command
       line  variable assignment is most useful for dynamically assigning val-
       ues to the variables AWK uses to  control  how  input  is  broken  into
       fields  and records.  It is also useful for controlling state if multi-
       ple passes are needed over a single data file.

       If the value of a particular element of ARGV is empty (""), gawk  skips
       over it.

       For  each  input  file,  if  a BEGINFILE rule exists, gawk executes the
       associated code before processing the contents of the file.  Similarly,
       gawk  executes  the  code  associated with ENDFILE after processing the

       For each record in the input, gawk tests to see if it matches any  pat-
       tern  in  the  AWK  program.  For each pattern that the record matches,
       gawk executes the associated action.  The patterns are  tested  in  the
       order they occur in the program.

       Finally,  after  all  the input is exhausted, gawk executes the code in
       the END rule(s) (if any).

   Command Line Directories
       According to POSIX, files named on the awk command line  must  be  text
       files.   The  behavior is ``undefined'' if they are not.  Most versions
       of awk treat a directory on the command line as a fatal error.

       Starting with version 4.0 of gawk, a directory on the command line pro-
       duces a warning, but is otherwise skipped.  If either of the --posix or
       --traditional options is given, then gawk reverts to treating  directo-
       ries on the command line as a fatal error.

       AWK variables are dynamic; they come into existence when they are first
       used.  Their values are either floating-point numbers  or  strings,  or
       both,  depending  upon  how  they  are used.  Additionally, gawk allows
       variables to have regular-expression type.  AWK  also  has  one  dimen-
       sional  arrays; arrays with multiple dimensions may be simulated.  Gawk
       provides true arrays of arrays; see Arrays, below.  Several pre-defined
       variables  are set as a program runs; these are described as needed and
       summarized below.

       Normally, records are separated by newline characters.  You can control
       how  records are separated by assigning values to the built-in variable
       RS.  If RS is any single character, that character  separates  records.
       Otherwise,  RS is a regular expression.  Text in the input that matches
       this regular expression separates the record.  However, in  compatibil-
       ity mode, only the first character of its string value is used for sep-
       arating records.  If RS is set to the null  string,  then  records  are
       separated  by empty lines.  When RS is set to the null string, the new-
       line character always acts as a field separator, in addition  to  what-
       ever value FS may have.

       As each input record is read, gawk splits the record into fields, using
       the value of the FS variable as the field separator.  If FS is a single
       character,  fields  are separated by that character.  If FS is the null
       string, then each individual character becomes a separate field.   Oth-
       erwise, FS is expected to be a full regular expression.  In the special
       case that FS is a single space, fields are separated by runs of  spaces
       and/or tabs and/or newlines.  NOTE: The value of IGNORECASE (see below)
       also affects how fields are split when FS is a regular expression,  and
       how records are separated when RS is a regular expression.

       If  the  FIELDWIDTHS  variable is set to a space-separated list of num-
       bers, each field is expected to have fixed width, and  gawk  splits  up
       the record using the specified widths.  Each field width may optionally
       be preceded by a colon-separated value specifying the number of charac-
       ters  to  skip  before  the  field starts.  The value of FS is ignored.
       Assigning a new value to FS or FPAT overrides the use of FIELDWIDTHS.

       Similarly, if the FPAT variable is set to a string representing a regu-
       lar expression, each field is made up of text that matches that regular
       expression. In this case, the regular expression describes  the  fields
       themselves, instead of the text that separates the fields.  Assigning a
       new value to FS or FIELDWIDTHS overrides the use of FPAT.

       Each field in the input record may be referenced by its  position:  $1,
       $2,  and so on.  $0 is the whole record.  Fields need not be referenced
       by constants:

              n = 5
              print $n

       prints the fifth field in the input record.

       The variable NF is set to the total  number  of  fields  in  the  input

       References  to non-existent fields (i.e., fields after $NF) produce the
       null-string.  However, assigning to a non-existent field (e.g., $(NF+2)
       = 5) increases the value of NF, creates any intervening fields with the
       null string as their values, and causes the value of $0  to  be  recom-
       puted, with the fields being separated by the value of OFS.  References
       to negative numbered fields  cause  a  fatal  error.   Decrementing  NF
       causes  the  values  of  fields  past the new value to be lost, and the
       value of $0 to be recomputed, with the fields being  separated  by  the
       value of OFS.

       Assigning  a  value  to an existing field causes the whole record to be
       rebuilt when $0 is referenced.  Similarly,  assigning  a  value  to  $0
       causes the record to be resplit, creating new values for the fields.

   Built-in Variables
       Gawk's built-in variables are:

       ARGC        The  number  of  command  line  arguments (does not include
                   options to gawk, or the program source).

       ARGIND      The index in ARGV of the current file being processed.

       ARGV        Array of command line arguments.  The array is indexed from
                   0  to  ARGC - 1.  Dynamically changing the contents of ARGV
                   can control the files used for data.

       BINMODE     On non-POSIX systems, specifies use of  "binary"  mode  for
                   all  file  I/O.  Numeric values of 1, 2, or 3, specify that
                   input files, output  files,  or  all  files,  respectively,
                   should  use binary I/O.  String values of "r", or "w" spec-
                   ify that input files, or output files, respectively, should
                   use binary I/O.  String values of "rw" or "wr" specify that
                   all files should use binary I/O.  Any other string value is
                   treated as "rw", but generates a warning message.

       CONVFMT     The conversion format for numbers, "%.6g", by default.

       ENVIRON     An  array containing the values of the current environment.
                   The array is indexed by  the  environment  variables,  each
                   element  being  the  value  of  that  variable (e.g., ENVI-
                   RON["HOME"] might be "/home/arnold").

                   In POSIX mode, changing this  array  does  not  affect  the
                   environment  seen  by  programs which gawk spawns via redi-
                   rection or the system() function.  Otherwise, gawk  updates
                   its  real  environment  so  that programs it spawns see the

       ERRNO       If a system error occurs either  doing  a  redirection  for
                   getline,  during  a  read for getline, or during a close(),
                   then ERRNO is set to a string describing  the  error.   The
                   value is subject to translation in non-English locales.  If
                   the string in ERRNO corresponds to a system  error  in  the
                   errno(3)  variable,  then the numeric value can be found in
                   PROCINFO["errno"].       For       non-system       errors,
                   PROCINFO["errno"] will be zero.

       FIELDWIDTHS A  whitespace-separated  list  of  field widths.  When set,
                   gawk parses the input into fields of fixed  width,  instead
                   of  using the value of the FS variable as the field separa-
                   tor.  Each field width may  optionally  be  preceded  by  a
                   colon-separated  value  specifying the number of characters
                   to skip before the field starts.  See Fields, above.

       FILENAME    The name of the current input file.  If no files are speci-
                   fied  on  the  command  line, the value of FILENAME is "-".
                   However,  FILENAME  is  undefined  inside  the  BEGIN  rule
                   (unless set by getline).

       FNR         The input record number in the current input file.

       FPAT        A  regular expression describing the contents of the fields
                   in a record.  When set, gawk parses the input into  fields,
                   where  the  fields match the regular expression, instead of
                   using the value of the FS variable as the field  separator.
                   See Fields, above.

       FS          The input field separator, a space by default.  See Fields,

       FUNCTAB     An array whose indices and  corresponding  values  are  the
                   names of all the user-defined or extension functions in the
                   program.  NOTE: You may not use the delete  statement  with
                   the FUNCTAB array.

       IGNORECASE  Controls the case-sensitivity of all regular expression and
                   string operations.  If IGNORECASE  has  a  non-zero  value,
                   then  string  comparisons  and  pattern  matching in rules,
                   field splitting with FS and FPAT,  record  separating  with
                   RS, regular expression matching with ~ and !~, and the gen-
                   sub(), gsub(), index(), match(), patsplit(),  split(),  and
                   sub() built-in functions all ignore case when doing regular
                   expression operations.  NOTE:  Array  subscripting  is  not
                   affected.   However, the asort() and asorti() functions are
                   Thus, if IGNORECASE is not equal to zero, /aB/ matches  all
                   of the strings "ab", "aB", "Ab", and "AB".  As with all AWK
                   variables, the initial value of IGNORECASE is zero, so  all
                   regular expression and string operations are normally case-

       LINT        Provides dynamic control of the --lint option  from  within
                   an AWK program.  When true, gawk prints lint warnings. When
                   false,  it  does  not.   When  assigned  the  string  value
                   "fatal",  lint  warnings  become fatal errors, exactly like
                   --lint=fatal.  Any other true value just prints warnings.

       NF          The number of fields in the current input record.

       NR          The total number of input records seen so far.

       OFMT        The output format for numbers, "%.6g", by default.

       OFS         The output field separator, a space by default.

       ORS         The output record separator, by default a newline.

       PREC        The working precision of arbitrary precision floating-point
                   numbers, 53 by default.

       PROCINFO    The  elements  of  this array provide access to information
                   about the running AWK program.  On some systems, there  may
                   be  elements  in  the  array, "group1" through "groupn" for
                   some n, which is the number of  supplementary  groups  that
                   the  process  has.   Use  the in operator to test for these
                   elements.  The following  elements  are  guaranteed  to  be

                   PROCINFO["argv"]     The command line arguments as received
                                        by gawk at the C-language level.   The
                                        subscripts start from zero.

                   PROCINFO["egid"]     The  value  of  the  getegid(2) system

                   PROCINFO["errno"]    The value of errno(3)  when  ERRNO  is
                                        set to the associated error message.

                   PROCINFO["euid"]     The  value  of  the  geteuid(2) system

                   PROCINFO["FS"]       "FS" if field splitting with FS is  in
                                        effect, "FPAT" if field splitting with
                                        FPAT is in  effect,  "FIELDWIDTHS"  if
                                        field splitting with FIELDWIDTHS is in
                                        effect, or "API" if API  input  parser
                                        field splitting is in effect.

                   PROCINFO["gid"]      The  value  of  the  getgid(2)  system

                                        A subarray, indexed by  the  names  of
                                        all  identifiers  used  in the text of
                                        the AWK program.  The values  indicate
                                        what  gawk knows about the identifiers
                                        after it has finished parsing the pro-
                                        gram;  they  are not updated while the
                                        program runs.   For  each  identifier,
                                        the value of the element is one of the

                                        "array"     The   identifier   is   an

                                        "builtin"   The identifier is a built-
                                                    in function.

                                        "extension" The   identifier   is   an
                                                    extension  function loaded
                                                    via @load or -l.

                                        "scalar"    The   identifier   is    a

                                        "untyped"   The  identifier is untyped
                                                    (could be used as a scalar
                                                    or   array,  gawk  doesn't
                                                    know yet).

                                        "user"      The identifier is a  user-
                                                    defined function.

                   PROCINFO["pgrpid"]   The  process  group  ID of the current

                   PROCINFO["pid"]      The process ID of the current process.

                   PROCINFO["ppid"]     The parent process ID of  the  current

                   PROCINFO["strftime"] The  default  time  format  string for

                   PROCINFO["uid"]      The  value  of  the  getuid(2)  system

                   PROCINFO["version"]  the version of gawk.

                   The  following  elements  are  present  if  loading dynamic
                   extensions is available:

                          The major version of the extension API.

                          The minor version of the extension API.

                   The following elements are available  if  MPFR  support  is
                   compiled into gawk:

                          The version of the GNU MP library used for arbitrary
                          precision number support in gawk.

                          The version of the GNU MPFR library used  for  arbi-
                          trary precision number support in gawk.

                          The  maximum  precision  supported  by  the GNU MPFR
                          library for arbitrary precision floating-point  num-

                          The  minimum  precision  allowed  by  the  GNU  MPFR
                          library for arbitrary precision floating-point  num-

                   The  following  elements  may  set  by  a program to change
                   gawk's behavior:

                          If this exists, then I/O errors for all redirections
                          become nonfatal.

                   PROCINFO["ame", "NONFATAL"]
                          Make I/O errors for name be nonfatal.

                   PROCINFO["command", "pty"]
                          Use a pseudo-tty for two-way communication with com-
                          mand instead of setting up two one-way pipes.

                   PROCINFO["input", "READ_TIMEOUT"]
                          The timeout in milliseconds for  reading  data  from
                          input,  where  input  is  a  redirection string or a
                          filename. A value of zero or less than zero means no

                   PROCINFO["input", "RETRY"]
                          If  an  I/O  error  that  may be retried occurs when
                          reading  data  from  input,  and  this  array  entry
                          exists, then getline returns -2 instead of following
                          the default behavior of returning -1 and configuring
                          input  to return no further data.  An I/O error that
                          may be retried is one where errno(3) has  the  value
                          EAGAIN,  EWOULDBLOCK, EINTR, or ETIMEDOUT.  This may
                          be  useful  in  conjunction  with  PROCINFO["input",
                          "READ_TIMEOUT"]  or situations where a file descrip-
                          tor has been configured to behave in a  non-blocking

                          If  this  element exists in PROCINFO, then its value
                          controls the order in which array elements are  tra-
                          versed   in   for   loops.    Supported  values  are
                          "@ind_str_asc",   "@ind_num_asc",   "@val_type_asc",
                          "@val_str_asc",   "@val_num_asc",   "@ind_str_desc",
                          "@ind_num_desc", "@val_type_desc",  "@val_str_desc",
                          "@val_num_desc",  and  "@unsorted".   The  value can
                          also be the name (as a  string)  of  any  comparison
                          function defined as follows:

                               function cmp_func(i1, v1, i2, v2)

                          where  i1  and i2 are the indices, and v1 and v2 are
                          the corresponding values of the two  elements  being
                          compared.   It  should  return  a  number less than,
                          equal to, or greater than 0, depending  on  how  the
                          elements of the array are to be ordered.

       ROUNDMODE   The rounding mode to use for arbitrary precision arithmetic
                   on numbers, by default "N" (IEEE-754 roundTiesToEven mode).
                   The accepted values are "N" or "n" for roundTiesToEven, "U"
                   or "u" for roundTowardPositive, "D" or "d" for roundToward-
                   Negative,  "Z" or "z" for roundTowardZero, and if your ver-
                   sion of GNU MPFR library supports it, "A" or "a" for round-
                   ing away from zero.

       RS          The input record separator, by default a newline.

       RT          The record terminator.  Gawk sets RT to the input text that
                   matched the character or regular  expression  specified  by

       RSTART      The  index  of the first character matched by match(); 0 if
                   no match.  (This implies that character  indices  start  at

       RLENGTH     The  length  of  the  string  matched  by match(); -1 if no

       SUBSEP      The character used to separate multiple subscripts in array
                   elements, by default "\034".

       SYMTAB      An  array  whose  indices  are  the  names of all currently
                   defined global variables and arrays in  the  program.   The
                   array  may be used for indirect access to read or write the
                   value of a variable:

                        foo = 5
                        SYMTAB["foo"] = 4
                        print foo    # prints 4

                   The typeof() function may be used to test if an element  in
                   SYMTAB  is  an array.  You may not use the delete statement
                   with the SYMTAB array.

       TEXTDOMAIN  The text domain of the AWK program; used to find the local-
                   ized translations for the program's strings.

       Arrays  are  subscripted  with an expression between square brackets ([
       and ]).  If the expression is an expression list (expr, expr ...)  then
       the  array subscript is a string consisting of the concatenation of the
       (string) value of each expression, separated by the value of the SUBSEP
       variable.   This  facility  is  used  to  simulate multiply dimensioned
       arrays.  For example:

              i = "A"; j = "B"; k = "C"
              x[i, j, k] = "hello, world\n"

       assigns the string "hello, world\n" to the element of the array x which
       is indexed by the string "A\034B\034C".  All arrays in AWK are associa-
       tive, i.e., indexed by string values.

       The special operator in may be used to test if an array  has  an  index
       consisting of a particular value:

              if (val in array)
                   print array[val]

       If the array has multiple subscripts, use (i, j) in array.

       The in construct may also be used in a for loop to iterate over all the
       elements of an array.  However, the (i,  j)  in  array  construct  only
       works in tests, not in for loops.

       An  element  may  be  deleted from an array using the delete statement.
       The delete statement may also be used to delete the entire contents  of
       an array, just by specifying the array name without a subscript.

       gawk  supports  true  multidimensional arrays. It does not require that
       such arrays be ``rectangular'' as in C or C++.  For example:

              a[1] = 5
              a[2][1] = 6
              a[2][2] = 7

       NOTE: You may need to tell gawk that an array element is really a  sub-
       array  in  order  to use it where gawk expects an array (such as in the
       second argument to split()).  You can do this by creating an element in
       the subarray and then deleting it with the delete statement.

   Variable Typing And Conversion
       Variables  and  fields  may be (floating point) numbers, or strings, or
       both.  They may also be regular expressions. How the value of  a  vari-
       able  is  interpreted  depends  upon its context.  If used in a numeric
       expression, it will be treated as a number; if used as a string it will
       be treated as a string.

       To force a variable to be treated as a number, add zero to it; to force
       it to be treated as a string, concatenate it with the null string.

       Uninitialized variables have the numeric  value  zero  and  the  string
       value "" (the null, or empty, string).

       When  a  string must be converted to a number, the conversion is accom-
       plished using strtod(3).  A number is converted to a  string  by  using
       the  value  of  CONVFMT  as  a  format  string for sprintf(3), with the
       numeric value of the variable as the argument.   However,  even  though
       all  numbers in AWK are floating-point, integral values are always con-
       verted as integers.  Thus, given

              CONVFMT = "%2.2f"
              a = 12
              b = a ""

       the variable b has a string value of "12" and not "12.00".

       NOTE: When operating in POSIX mode (such as with the  --posix  option),
       beware  that locale settings may interfere with the way decimal numbers
       are treated: the decimal separator of the numbers you  are  feeding  to
       gawk  must  conform to what your locale would expect, be it a comma (,)
       or a period (.).

       Gawk performs comparisons as follows: If  two  variables  are  numeric,
       they  are  compared numerically.  If one value is numeric and the other
       has a string value that is a "numeric  string,"  then  comparisons  are
       also  done numerically.  Otherwise, the numeric value is converted to a
       string and a string comparison is performed.  Two strings are compared,
       of course, as strings.

       Note that string constants, such as "57", are not numeric strings, they
       are string constants.  The idea of "numeric  string"  only  applies  to
       fields,  getline  input,  FILENAME, ARGV elements, ENVIRON elements and
       the elements of an array created by  split()  or  patsplit()  that  are
       numeric  strings.   The  basic  idea  is that user input, and only user
       input, that looks numeric, should be treated that way.

   Octal and Hexadecimal Constants
       You may use C-style octal and hexadecimal constants in your AWK program
       source  code.   For example, the octal value 011 is equal to decimal 9,
       and the hexadecimal value 0x11 is equal to decimal 17.

   String Constants
       String constants in AWK are sequences of  characters  enclosed  between
       double quotes (like "value").  Within strings, certain escape sequences
       are recognized, as in C.  These are:

       \\   A literal backslash.

       \a   The "alert" character; usually the ASCII BEL character.

       \b   Backspace.

       \f   Form-feed.

       \n   Newline.

       \r   Carriage return.

       \t   Horizontal tab.

       \v   Vertical tab.

       \xhex digits
            The character represented by the string of hexadecimal digits fol-
            lowing the \x.  Up to two following hexadecimal digits are consid-
            ered part of the escape sequence.  E.g., "\x1B" is the  ASCII  ESC
            (escape) character.

       \ddd The  character  represented  by the 1-, 2-, or 3-digit sequence of
            octal digits.  E.g., "\033" is the ASCII ESC (escape) character.

       \c   The literal character c.

       In compatibility mode, the characters represented by octal and hexadec-
       imal  escape  sequences  are  treated  literally  when  used in regular
       expression constants.  Thus, /a\52b/ is equivalent to /a\*b/.

   Regexp Constants
       A regular expression constant is  a  sequence  of  characters  enclosed
       between forward slashes (like /value/).  Regular expression matching is
       described more fully below; see Regular Expressions.

       The escape sequences described earlier may also be used inside constant
       regular  expressions  (e.g., /[ \t\f\n\r\v]/ matches whitespace charac-

       Gawk   provides strongly typed regular expression constants. These  are
              written  with a leading @ symbol (like so: @/value/).  Such con-
              stants may be assigned to scalars  (variables,  array  elements)
              and  passed  to user-defined functions. Variables that have been
              so assigned have regular expression type.

       AWK is a line-oriented language.  The pattern comes first, and then the
       action.  Action statements are enclosed in { and }.  Either the pattern
       may be missing, or the action may be missing, but, of course, not both.
       If  the pattern is missing, the action executes for every single record
       of input.  A missing action is equivalent to

              { print }

       which prints the entire record.

       Comments begin with the # character, and continue until the end of  the
       line.   Empty  lines  may  be used to separate statements.  Normally, a
       statement ends with a newline, however, this is not the case for  lines
       ending in a comma, {, ?, :, &&, or ||.  Lines ending in do or else also
       have their statements automatically continued on  the  following  line.
       In  other  cases,  a  line can be continued by ending it with a "\", in
       which case the newline is ignored.

       Multiple statements may be put on one line by separating  them  with  a
       ";".   This  applies to both the statements within the action part of a
       pattern-action pair (the usual case), and to the pattern-action  state-
       ments themselves.

       AWK patterns may be one of the following:

              /regular expression/
              relational expression
              pattern && pattern
              pattern || pattern
              pattern ? pattern : pattern
              ! pattern
              pattern1, pattern2

       BEGIN  and  END  are two special kinds of patterns which are not tested
       against the input.  The action parts of all BEGIN patterns  are  merged
       as if all the statements had been written in a single BEGIN rule.  They
       are executed before any of the input is read.  Similarly, all  the  END
       rules are merged, and executed when all the input is exhausted (or when
       an exit statement is executed).  BEGIN and END patterns cannot be  com-
       bined  with  other patterns in pattern expressions.  BEGIN and END pat-
       terns cannot have missing action parts.

       BEGINFILE and ENDFILE are additional special patterns whose bodies  are
       executed  before  reading  the  first record of each command line input
       file and after reading the last record of each file.  Inside the BEGIN-
       FILE  rule,  the  value  of  ERRNO  is the empty string if the file was
       opened successfully.  Otherwise, there is some problem  with  the  file
       and  the code should use nextfile to skip it. If that is not done, gawk
       produces its usual fatal error for files that cannot be opened.

       For /regular expression/ patterns, the associated statement is executed
       for  each  input  record  that matches the regular expression.  Regular
       expressions are the same as  those  in  egrep(1),  and  are  summarized

       A  relational  expression may use any of the operators defined below in
       the section on actions.  These generally test  whether  certain  fields
       match certain regular expressions.

       The  &&,  ||, and !  operators are logical AND, logical OR, and logical
       NOT, respectively, as in C.  They do short-circuit evaluation, also  as
       in  C,  and  are used for combining more primitive pattern expressions.
       As in most languages, parentheses may be used to change  the  order  of

       The  ?:  operator is like the same operator in C.  If the first pattern
       is true then the pattern used for testing is the second pattern, other-
       wise  it  is  the  third.  Only one of the second and third patterns is

       The pattern1, pattern2 form of an expression is called a range pattern.
       It  matches  all input records starting with a record that matches pat-
       tern1, and continuing until a record that matches pattern2,  inclusive.
       It does not combine with any other sort of pattern expression.

   Regular Expressions
       Regular  expressions  are  the  extended kind found in egrep.  They are
       composed of characters as follows:

       c          Matches the non-metacharacter c.

       \c         Matches the literal character c.

       .          Matches any character including newline.

       ^          Matches the beginning of a string.

       $          Matches the end of a string.

       [abc...]   A character list: matches any of the characters abc....  You
                  may  include a range of characters by separating them with a

       [^abc...]  A negated  character  list:  matches  any  character  except

       r1|r2      Alternation: matches either r1 or r2.

       r1r2       Concatenation: matches r1, and then r2.

       r+         Matches one or more r's.

       r*         Matches zero or more r's.

       r?         Matches zero or one r's.

       (r)        Grouping: matches r.

       r{n,m}     One  or two numbers inside braces denote an interval expres-
                  sion.  If there is one number in the braces,  the  preceding
                  regular  expression r is repeated n times.  If there are two
                  numbers separated by a comma, r is repeated n  to  m  times.
                  If  there  is  one  number  followed  by  a comma, then r is
                  repeated at least n times.

       \y         Matches the empty string at either the beginning or the  end
                  of a word.

       \B         Matches the empty string within a word.

       \<         Matches the empty string at the beginning of a word.

       \>         Matches the empty string at the end of a word.

       \s         Matches any whitespace character.

       \S         Matches any nonwhitespace character.

       \w         Matches  any  word-constituent  character (letter, digit, or

       \W         Matches any character that is not word-constituent.

       \`         Matches the empty  string  at  the  beginning  of  a  buffer

       \'         Matches the empty string at the end of a buffer.

       The  escape  sequences  that  are valid in string constants (see String
       Constants) are also valid in regular expressions.

       Character classes are a feature introduced in the  POSIX  standard.   A
       character  class  is a special notation for describing lists of charac-
       ters that have a specific attribute, but where  the  actual  characters
       themselves  can  vary from country to country and/or from character set
       to character set.  For example, the notion of  what  is  an  alphabetic
       character differs in the USA and in France.

       A  character  class  is  only  valid in a regular expression inside the
       brackets of a character list.  Character classes consist of [:, a  key-
       word  denoting the class, and :].  The character classes defined by the
       POSIX standard are:

       [:alnum:]  Alphanumeric characters.

       [:alpha:]  Alphabetic characters.

       [:blank:]  Space or tab characters.

       [:cntrl:]  Control characters.

       [:digit:]  Numeric characters.

       [:graph:]  Characters that are both printable and visible.  (A space is
                  printable, but not visible, while an a is both.)

       [:lower:]  Lowercase alphabetic characters.

       [:print:]  Printable  characters (characters that are not control char-

       [:punct:]  Punctuation characters (characters that are not letter, dig-
                  its, control characters, or space characters).

       [:space:]  Space  characters (such as space, tab, and formfeed, to name
                  a few).

       [:upper:]  Uppercase alphabetic characters.

       [:xdigit:] Characters that are hexadecimal digits.

       For example, before the POSIX standard, to match  alphanumeric  charac-
       ters, you would have had to write /[A-Za-z0-9]/.  If your character set
       had other alphabetic characters in it, this would not match  them,  and
       if  your  character set collated differently from ASCII, this might not
       even match the ASCII alphanumeric characters.  With the POSIX character
       classes,  you  can write /[[:alnum:]]/, and this matches the alphabetic
       and numeric characters in your character set, no matter what it is.

       Two additional special sequences can appear in character lists.   These
       apply  to  non-ASCII  character  sets,  which  can  have single symbols
       (called collating elements) that are represented  with  more  than  one
       character,  as  well as several characters that are equivalent for col-
       lating, or sorting, purposes.  (E.g., in French,  a  plain  "e"  and  a
       grave-accented "`" are equivalent.)

       Collating Symbols
              A  collating  symbol  is  a  multi-character  collating  element
              enclosed in [.  and .].  For example, if ch is a collating  ele-
              ment,  then  [[.ch.]]  is a regular expression that matches this
              collating element, while  [ch]  is  a  regular  expression  that
              matches either c or h.

       Equivalence Classes
              An  equivalence  class  is  a locale-specific name for a list of
              characters that are equivalent.  The name is enclosed in [=  and
              =].   For  example, the name e might be used to represent all of
              "e", "'", and "`".  In this case, [[=e=]] is a  regular  expres-
              sion that matches any of e, ', or `.

       These  features are very valuable in non-English speaking locales.  The
       library functions that gawk uses for regular expression  matching  cur-
       rently  only  recognize  POSIX character classes; they do not recognize
       collating symbols or equivalence classes.

       The \y, \B, \<, \>, \s, \S, \w, \W, \`, and \' operators  are  specific
       to  gawk;  they  are  extensions based on facilities in the GNU regular
       expression libraries.

       The various command line options control how gawk interprets characters
       in regular expressions.

       No options
              In  the  default case, gawk provides all the facilities of POSIX
              regular expressions and the  GNU  regular  expression  operators
              described above.

              Only  POSIX regular expressions are supported, the GNU operators
              are not special.  (E.g., \w matches a literal w).

              Traditional UNIX awk regular expressions are matched.   The  GNU
              operators  are  not  special,  and  interval expressions are not
              available.  Characters described by octal and hexadecimal escape
              sequences  are treated literally, even if they represent regular
              expression metacharacters.

              Allow interval  expressions  in  regular  expressions,  even  if
              --traditional has been provided.

       Action  statements  are enclosed in braces, { and }.  Action statements
       consist of the usual assignment, conditional,  and  looping  statements
       found  in  most  languages.   The  operators,  control  statements, and
       input/output statements available are patterned after those in C.

       The operators in AWK, in order of decreasing precedence, are:

       (...)       Grouping

       $           Field reference.

       ++ --       Increment and decrement, both prefix and postfix.

       ^           Exponentiation (** may  also  be  used,  and  **=  for  the
                   assignment operator).

       + - !       Unary plus, unary minus, and logical negation.

       * / %       Multiplication, division, and modulus.

       + -         Addition and subtraction.

       space       String concatenation.

       |   |&      Piped I/O for getline, print, and printf.

       < > <= >= == !=
                   The regular relational operators.

       ~ !~        Regular  expression match, negated match.  NOTE: Do not use
                   a constant regular expression (/foo/) on the left-hand side
                   of  a  ~  or !~.  Only use one on the right-hand side.  The
                   expression /foo/ ~ exp has  the  same  meaning  as  (($0  ~
                   /foo/) ~ exp).  This is usually not what you want.

       in          Array membership.

       &&          Logical AND.

       ||          Logical OR.

       ?:          The  C  conditional  expression.  This has the form expr1 ?
                   expr2 : expr3.  If expr1 is true, the value of the  expres-
                   sion  is  expr2,  otherwise it is expr3.  Only one of expr2
                   and expr3 is evaluated.

       = += -= *= /= %= ^=
                   Assignment.  Both absolute assignment  (var  =  value)  and
                   operator-assignment (the other forms) are supported.

   Control Statements
       The control statements are as follows:

              if (condition) statement [ else statement ]
              while (condition) statement
              do statement while (condition)
              for (expr1; expr2; expr3) statement
              for (var in array) statement
              delete array[index]
              delete array
              exit [ expression ]
              { statements }
              switch (expression) {
              case value|regex : statement
              [ default: statement ]

   I/O Statements
       The input/output statements are as follows:

       close(file [, how])   Close  file, pipe or coprocess.  The optional how
                             should only be used when closing  one  end  of  a
                             two-way pipe to a coprocess.  It must be a string
                             value, either "to" or "from".

       getline               Set $0 from next input record; set NF,  NR,  FNR,

       getline <file         Set $0 from next record of file; set NF, RT.

       getline var           Set var from next input record; set NR, FNR, RT.

       getline var <file     Set var from next record of file, RT.

       command | getline [var]
                             Run  command  piping the output either into $0 or
                             var, as above, and RT.

       command |& getline [var]
                             Run command as  a  coprocess  piping  the  output
                             either  into $0 or var, as above, and RT.  Copro-
                             cesses are a gawk extension.  (command  can  also
                             be  a  socket.   See  the subsection Special File
                             Names, below.)

       next                  Stop processing the current  input  record.   The
                             next  input  record is read and processing starts
                             over with the first pattern in the  AWK  program.
                             Upon  reaching  the  end  of the input data, gawk
                             executes any END rule(s).

       nextfile              Stop processing the current input file.  The next
                             input record read comes from the next input file.
                             FILENAME and ARGIND are updated, FNR is reset  to
                             1, and processing starts over with the first pat-
                             tern in the AWK program.  Upon reaching  the  end
                             of  the input data, gawk executes any ENDFILE and
                             END rule(s).

       print                 Print the current record.  The output  record  is
                             terminated with the value of ORS.

       print expr-list       Print  expressions.  Each expression is separated
                             by the value of OFS.  The output record is termi-
                             nated with the value of ORS.

       print expr-list >file Print  expressions  on  file.  Each expression is
                             separated by the value of OFS.  The output record
                             is terminated with the value of ORS.

       printf fmt, expr-list Format  and  print.   See  The  printf Statement,

       printf fmt, expr-list >file
                             Format and print on file.

       system(cmd-line)      Execute the command cmd-line, and return the exit
                             status.   (This may not be available on non-POSIX
                             systems.)  See GAWK:  Effective  AWK  Programming
                             for the full details on the exit status.

       fflush([file])        Flush any buffers associated with the open output
                             file or pipe file.  If file is missing or  if  it
                             is  the  null  string, then flush all open output
                             files and pipes.

       Additional output redirections are allowed for print and printf.

       print ... >> file
              Appends output to the file.

       print ... | command
              Writes on a pipe.

       print ... |& command
              Sends data to a coprocess or socket.  (See also  the  subsection
              Special File Names, below.)

       The  getline  command returns 1 on success, zero on end of file, and -1
       on an error.  If the errno(3) value indicates that  the  I/O  operation
       may  be  retried,  and  PROCINFO["input",  "RETRY"]  is set, then -2 is
       returned instead of -1, and further calls to getline may be  attempted.
       Upon an error, ERRNO is set to a string describing the problem.

       NOTE:  Failure in opening a two-way socket results in a non-fatal error
       being returned to the calling function. If using a pipe, coprocess,  or
       socket  to getline, or from print or printf within a loop, you must use
       close() to create new instances of the command or socket.  AWK does not
       automatically  close  pipes,  sockets,  or coprocesses when they return

   The printf Statement
       The AWK versions of the printf statement and  sprintf()  function  (see
       below) accept the following conversion specification formats:

       %c      A single character.  If the argument used for %c is numeric, it
               is treated as a character and printed.  Otherwise, the argument
               is assumed to be a string, and the only first character of that
               string is printed.

       %d, %i  A decimal number (the integer part).

       %e, %E  A floating point number of the form [-]d.dddddde[+-]dd.  The %E
               format uses E instead of e.

       %f, %F  A floating point number of the form [-]ddd.dddddd.  If the sys-
               tem library supports it, %F is available as well. This is  like
               %f,  but  uses  capital  letters for special "not a number" and
               "infinity" values. If %F is not available, gawk uses %f.

       %g, %G  Use %e or %f conversion, whichever is shorter, with nonsignifi-
               cant zeros suppressed.  The %G format uses %E instead of %e.

       %o      An unsigned octal number (also an integer).

       %u      An unsigned decimal number (again, an integer).

       %s      A character string.

       %x, %X  An  unsigned  hexadecimal  number  (an integer).  The %X format
               uses ABCDEF instead of abcdef.

       %%      A single % character; no argument is converted.

       Optional, additional parameters may lie between the % and  the  control

       count$ Use the count'th argument at this point in the formatting.  This
              is called a positional specifier and is intended  primarily  for
              use  in translated versions of format strings, not in the origi-
              nal text of an AWK program.  It is a gawk extension.

       -      The expression should be left-justified within its field.

       space  For numeric conversions, prefix positive values  with  a  space,
              and negative values with a minus sign.

       +      The  plus sign, used before the width modifier (see below), says
              to always supply a sign for numeric  conversions,  even  if  the
              data  to  be  formatted  is positive.  The + overrides the space

       #      Use an "alternate form" for certain control  letters.   For  %o,
              supply  a  leading zero.  For %x, and %X, supply a leading 0x or
              0X for a nonzero result.  For %e, %E,  %f  and  %F,  the  result
              always contains a decimal point.  For %g, and %G, trailing zeros
              are not removed from the result.

       0      A leading 0 (zero) acts as a flag, indicating that output should
              be  padded  with zeroes instead of spaces.  This applies only to
              the numeric output formats.  This flag only has an  effect  when
              the field width is wider than the value to be printed.

       '      A  single  quote character instructs gawk to insert the locale's
              thousands-separator character into decimal numbers, and to  also
              use  the  locale's  decimal  point character with floating point
              formats.  This requires correct locale support in the C  library
              and in the definition of the current locale.

       width  The field should be padded to this width.  The field is normally
              padded with spaces.  With the 0 flag, it is padded with zeroes.

       .prec  A number that specifies the precision to use when printing.  For
              the  %e,  %E,  %f  and %F, formats, this specifies the number of
              digits you want printed to the right of the decimal point.   For
              the  %g, and %G formats, it specifies the maximum number of sig-
              nificant digits.  For the %d, %i, %o, %u, %x, and %X formats, it
              specifies  the  minimum  number  of digits to print.  For %s, it
              specifies the maximum number of characters from the string  that
              should be printed.

       The  dynamic width and prec capabilities of the ISO C printf() routines
       are supported.  A * in place of either the width or prec specifications
       causes  their  values  to  be taken from the argument list to printf or
       sprintf().  To use a positional specifier with a dynamic width or  pre-
       cision,  supply the count$ after the * in the format string.  For exam-
       ple, "%3$*2$.*1$s".

   Special File Names
       When doing I/O redirection from either print or printf into a file,  or
       via  getline  from  a  file,  gawk recognizes certain special filenames
       internally.  These filenames allow  access  to  open  file  descriptors
       inherited  from  gawk's parent process (usually the shell).  These file
       names may also be used on the command line to  name  data  files.   The
       filenames are:

       -           The standard input.

       /dev/stdin  The standard input.

       /dev/stdout The standard output.

       /dev/stderr The standard error output.

       /dev/fd/n   The file associated with the open file descriptor n.

       These are particularly useful for error messages.  For example:

              print "You blew it!" > "/dev/stderr"

       whereas you would otherwise have to use

              print "You blew it!" | "cat 1>&2"

       The following special filenames may be used with the |& coprocess oper-
       ator for creating TCP/IP network connections:

              Files for a TCP/IP connection on local port lport to remote host
              rhost  on remote port rport.  Use a port of 0 to have the system
              pick a port.  Use /inet4 to force an IPv4 connection, and /inet6
              to  force  an  IPv6  connection.   Plain  /inet  uses the system
              default (most likely IPv4).

              Similar, but use UDP/IP instead of TCP/IP.

   Numeric Functions
       AWK has the following built-in arithmetic functions:

       atan2(y, x)   Return the arctangent of y/x in radians.

       cos(expr)     Return the cosine of expr, which is in radians.

       exp(expr)     The exponential function.

       int(expr)     Truncate to integer.

       log(expr)     The natural logarithm function.

       rand()        Return a random number N, between zero and one, such that
                     0 <= N < 1.

       sin(expr)     Return the sine of expr, which is in radians.

       sqrt(expr)    Return the square root of expr.

       srand([expr]) Use expr as the new seed for the random number generator.
                     If no expr is provided, use the time of day.  Return  the
                     previous seed for the random number generator.

   String Functions
       Gawk has the following built-in string functions:

       asort(s [, d [, how] ]) Return  the  number  of  elements in the source
                               array s.  Sort the contents of s  using  gawk's
                               normal  rules for comparing values, and replace
                               the indices of the sorted values s with sequen-
                               tial  integers starting with 1. If the optional
                               destination array d is specified, first  dupli-
                               cate  s  into  d,  and then sort d, leaving the
                               indices of the source array  s  unchanged.  The
                               optional  string how controls the direction and
                               the comparison mode.  Valid values for how  are
                               any     of     the     strings     valid    for
                               PROCINFO["sorted_in"].  It can also be the name
                               of   a   user-defined  comparison  function  as
                               described in PROCINFO["sorted_in"].

       asorti(s [, d [, how] ])
                               Return the number of  elements  in  the  source
                               array  s.   The behavior is the same as that of
                               asort(), except that the array indices are used
                               for  sorting, not the array values.  When done,
                               the array is indexed numerically, and the  val-
                               ues  are  those  of  the original indices.  The
                               original values are lost; thus provide a second
                               array  if  you  wish  to preserve the original.
                               The purpose of the optional string how  is  the
                               same as described previously for asort().

       gensub(r, s, h [, t])   Search  the  target string t for matches of the
                               regular expression r.  If h is a string  begin-
                               ning with g or G, then replace all matches of r
                               with s.  Otherwise, h is  a  number  indicating
                               which  match of r to replace.  If t is not sup-
                               plied, use $0 instead.  Within the  replacement
                               text  s,  the  sequence  \n, where n is a digit
                               from 1 to 9, may be used to indicate  just  the
                               text that matched the n'th parenthesized subex-
                               pression.   The  sequence  \0  represents   the
                               entire  matched  text, as does the character &.
                               Unlike sub() and gsub(), the modified string is
                               returned as the result of the function, and the
                               original target string is not changed.

       gsub(r, s [, t])        For each substring matching the regular expres-
                               sion  r  in the string t, substitute the string
                               s, and return the number of substitutions.   If
                               t  is  not  supplied,  use  $0.   An  &  in the
                               replacement text is replaced with the text that
                               was  actually matched.  Use \& to get a literal
                               &.  (This must be typed  as  "\\&";  see  GAWK:
                               Effective  AWK Programming for a fuller discus-
                               sion of the  rules  for  ampersands  and  back-
                               slashes  in  the  replacement  text  of  sub(),
                               gsub(), and gensub().)

       index(s, t)             Return the index of the string t in the  string
                               s,  or zero if t is not present.  (This implies
                               that character indices start at one.)  It is  a
                               fatal error to use a regexp constant for t.

       length([s])             Return  the  length  of  the  string  s, or the
                               length of $0 if s is not supplied.  As  a  non-
                               standard  extension,  with  an  array argument,
                               length() returns the number of elements in  the

       match(s, r [, a])       Return  the  position  in  s  where the regular
                               expression r  occurs,  or  zero  if  r  is  not
                               present,  and  set  the  values  of  RSTART and
                               RLENGTH.  Note that the argument order  is  the
                               same as for the ~ operator: str ~ re.  If array
                               a is provided, a is cleared and then elements 1
                               through  n  are  filled  with the portions of s
                               that match the corresponding parenthesized sub-
                               expression in r.  The zero'th element of a con-
                               tains the portion of s matched  by  the  entire
                               regular    expression   r.    Subscripts   a[n,
                               "start"], and a[n, "length"] provide the start-
                               ing  index  in  the  string  and length respec-
                               tively, of each matching substring.

       patsplit(s, a [, r [, seps] ])
                               Split the string s into the  array  a  and  the
                               separators array seps on the regular expression
                               r, and return the number  of  fields.   Element
                               values  are  the  portions of s that matched r.
                               The value of seps[i] is the possibly null sepa-
                               rator  that  appeared after a[i].  The value of
                               seps[0] is the possibly null leading separator.
                               If  r  is  omitted,  FPAT is used instead.  The
                               arrays a and seps are cleared first.  Splitting
                               behaves  identically  to  field  splitting with
                               FPAT, described above.

       split(s, a [, r [, seps] ])
                               Split the string s into the  array  a  and  the
                               separators array seps on the regular expression
                               r, and return the number of fields.   If  r  is
                               omitted,  FS is used instead.  The arrays a and
                               seps are cleared first.  seps[i] is  the  field
                               separator matched by r between a[i] and a[i+1].
                               If r is a single space, then leading whitespace
                               in  s goes into the extra array element seps[0]
                               and trailing whitespace  goes  into  the  extra
                               array  element  seps[n],  where n is the return
                               value  of  split(s,  a,  r,  seps).   Splitting
                               behaves   identically   to   field   splitting,
                               described above.

       sprintf(fmt, expr-list) Print expr-list according to  fmt,  and  return
                               the resulting string.

       strtonum(str)           Examine  str, and return its numeric value.  If
                               str begins with a leading 0,  treat  it  as  an
                               octal  number.  If str begins with a leading 0x
                               or 0X, treat it as a hexadecimal number.   Oth-
                               erwise, assume it is a decimal number.

       sub(r, s [, t])         Just  like  gsub(),  but replace only the first
                               matching substring.  Return either zero or one.

       substr(s, i [, n])      Return the at most n-character substring  of  s
                               starting  at  i.  If n is omitted, use the rest
                               of s.

       tolower(str)            Return a copy of the string str, with  all  the
                               uppercase characters in str translated to their
                               corresponding  lowercase  counterparts.    Non-
                               alphabetic characters are left unchanged.

       toupper(str)            Return  a  copy of the string str, with all the
                               lowercase characters in str translated to their
                               corresponding   uppercase  counterparts.   Non-
                               alphabetic characters are left unchanged.

       Gawk is multibyte aware.  This means that index(),  length(),  substr()
       and match() all work in terms of characters, not bytes.

   Time Functions
       Since  one  of the primary uses of AWK programs is processing log files
       that contain time stamp information, gawk provides the following  func-
       tions for obtaining time stamps and formatting them.

       mktime(datespec [, utc-flag])
                 Turn  datespec into a time stamp of the same form as returned
                 by systime(), and return  the  result.   The  datespec  is  a
                 string  of  the form YYYY MM DD HH MM SS[ DST].  The contents
                 of the string are six or seven numbers  representing  respec-
                 tively  the  full year including century, the month from 1 to
                 12, the day of the month from 1 to 31, the hour  of  the  day
                 from  0  to 23, the minute from 0 to 59, the second from 0 to
                 60, and an optional daylight  saving  flag.   The  values  of
                 these  numbers  need  not be within the ranges specified; for
                 example, an hour of -1 means 1  hour  before  midnight.   The
                 origin-zero  Gregorian  calendar is assumed, with year 0 pre-
                 ceding year 1 and year -1 preceding year 0.  If  utc-flag  is
                 present  and  is non-zero or non-null, the time is assumed to
                 be in the UTC time zone; otherwise, the time is assumed to be
                 in  the  local time zone.  If the DST daylight saving flag is
                 positive, the time is assumed to be daylight saving time;  if
                 zero,  the  time is assumed to be standard time; and if nega-
                 tive (the default), mktime() attempts  to  determine  whether
                 daylight saving time is in effect for the specified time.  If
                 datespec does not contain enough elements or if the resulting
                 time is out of range, mktime() returns -1.

       strftime([format [, timestamp[, utc-flag]]])
                 Format  timestamp  according  to the specification in format.
                 If utc-flag is present  and  is  non-zero  or  non-null,  the
                 result is in UTC, otherwise the result is in local time.  The
                 timestamp should be of the same  form  as  returned  by  sys-
                 time().   If timestamp is missing, the current time of day is
                 used.  If format is missing, a default format  equivalent  to
                 the  output of date(1) is used.  The default format is avail-
                 able in PROCINFO["strftime"].  See the specification for  the
                 strftime()  function in ISO C for the format conversions that
                 are guaranteed to be available.

       systime() Return the current time of day as the number of seconds since
                 the Epoch (1970-01-01 00:00:00 UTC on POSIX systems).

   Bit Manipulations Functions
       Gawk  supplies  the following bit manipulation functions.  They work by
       converting double-precision floating point values  to  uintmax_t  inte-
       gers,  doing  the  operation,  and  then  converting the result back to
       floating point.

       NOTE: Passing negative operands to any  of  these  functions  causes  a
       fatal error.

       The functions are:

       and(v1, v2 [, ...]) Return  the  bitwise  AND of the values provided in
                           the argument list.  There must be at least two.

       compl(val)          Return the bitwise complement of val.

       lshift(val, count)  Return the value of  val,  shifted  left  by  count

       or(v1, v2 [, ...])  Return the bitwise OR of the values provided in the
                           argument list.  There must be at least two.

       rshift(val, count)  Return the value of val,  shifted  right  by  count

       xor(v1, v2 [, ...]) Return  the  bitwise  XOR of the values provided in
                           the argument list.  There must be at least two.

   Type Functions
       The following function is for use with multidimensional arrays.

              Return true if x is an array, false otherwise.

       You can tell the type of any variable or array element with the follow-
       ing function:

              Return  a  string  indicating the type of x.  The string will be
              one of  "array",  "number",  "regexp",  "string",  "strnum",  or

   Internationalization Functions
       The  following  functions  may be used from within your AWK program for
       translating strings at run-time.  For full details, see GAWK: Effective
       AWK Programming.

       bindtextdomain(directory [, domain])
              Specify  the  directory  where gawk looks for the .gmo files, in
              case they will not or cannot be placed in the ``standard'' loca-
              tions  (e.g.,  during  testing).  It returns the directory where
              domain is ``bound.''
              The default domain is the value of TEXTDOMAIN.  If directory  is
              the  null string (""), then bindtextdomain() returns the current
              binding for the given domain.

       dcgettext(string [, domain [, category]])
              Return the translation of  string  in  text  domain  domain  for
              locale  category  category.  The default value for domain is the
              current value of TEXTDOMAIN.  The default value for category  is
              If you supply a value for category, it must be a string equal to
              one of the known locale categories described in GAWK:  Effective
              AWK  Programming.   You  must  also  supply  a text domain.  Use
              TEXTDOMAIN if you want to use the current domain.

       dcngettext(string1, string2, number [, domain [, category]])
              Return the plural form used for number  of  the  translation  of
              string1  and  string2  in text domain domain for locale category
              category.  The default value for domain is the current value  of
              TEXTDOMAIN.  The default value for category is "LC_MESSAGES".
              If you supply a value for category, it must be a string equal to
              one of the known locale categories described in GAWK:  Effective
              AWK  Programming.   You  must  also  supply  a text domain.  Use
              TEXTDOMAIN if you want to use the current domain.

       Functions in AWK are defined as follows:

              function name(parameter list) { statements }

       Functions execute when they  are  called  from  within  expressions  in
       either patterns or actions.  Actual parameters supplied in the function
       call are used to instantiate the  formal  parameters  declared  in  the
       function.   Arrays  are passed by reference, other variables are passed
       by value.

       Since functions were not originally part of the AWK language, the  pro-
       vision for local variables is rather clumsy: They are declared as extra
       parameters in the parameter list.  The convention is to separate  local
       variables  from  real parameters by extra spaces in the parameter list.
       For example:

              function  f(p, q,     a, b)   # a and b are local

              /abc/     { ... ; f(1, 2) ; ... }

       The left parenthesis in a function call is required to immediately fol-
       low the function name, without any intervening whitespace.  This avoids
       a syntactic ambiguity with the concatenation operator.   This  restric-
       tion does not apply to the built-in functions listed above.

       Functions  may  call each other and may be recursive.  Function parame-
       ters used as local variables are initialized to the null string and the
       number zero upon function invocation.

       Use return expr to return a value from a function.  The return value is
       undefined if no value is provided, or if the function returns by "fall-
       ing off" the end.

       As  a  gawk  extension, functions may be called indirectly. To do this,
       assign the name of the function to be called, as a string, to  a  vari-
       able.  Then use the variable as if it were the name of a function, pre-
       fixed with an @ sign, like so:
              function myfunc()
                   print "myfunc called"

              {    ...
                   the_func = "myfunc"
                   @the_func()    # call through the_func to myfunc
       As of version 4.1.2, this works with user-defined  functions,  built-in
       functions, and extension functions.

       If  --lint has been provided, gawk warns about calls to undefined func-
       tions at parse time, instead of at  run  time.   Calling  an  undefined
       function at run time is a fatal error.

       The word func may be used in place of function, although this is depre-

       You can dynamically add new built-in  functions  to  the  running  gawk
       interpreter  with the @load statement.  The full details are beyond the
       scope of this manual page; see GAWK: Effective AWK Programming.

       The gawk profiler accepts two signals.  SIGUSR1 causes  it  to  dump  a
       profile  and  function  call stack to the profile file, which is either
       awkprof.out, or whatever file was named with the --profile option.   It
       then  continues  to  run.   SIGHUP  causes gawk to dump the profile and
       function call stack and then exit.

       String constants are sequences of characters enclosed in double quotes.
       In non-English speaking environments, it is possible to mark strings in
       the AWK program as requiring translation to the local natural language.
       Such  strings  are  marked in the AWK program with a leading underscore
       ("_").  For example,

              gawk 'BEGIN { print "hello, world" }'

       always prints hello, world.  But,

              gawk 'BEGIN { print _"hello, world" }'

       might print bonjour, monde in France.

       There are several steps involved in producing and running a localizable
       AWK program.

       1.  Add  a BEGIN action to assign a value to the TEXTDOMAIN variable to
           set the text domain to a name associated with your program:

                BEGIN { TEXTDOMAIN = "myprog" }

           This allows gawk to find the .gmo file associated  with  your  pro-
           gram.  Without this step, gawk uses the messages text domain, which
           likely does not contain translations for your program.

       2.  Mark all strings that should  be  translated  with  leading  under-

       3.  If necessary, use the dcgettext() and/or bindtextdomain() functions
           in your program, as appropriate.

       4.  Run gawk --gen-pot -f myprog.awk > myprog.pot to  generate  a  .pot
           file for your program.

       5.  Provide  appropriate translations, and build and install the corre-
           sponding .gmo files.

       The internationalization features are described in full detail in GAWK:
       Effective AWK Programming.

       A  primary  goal  for gawk is compatibility with the POSIX standard, as
       well as with the latest version of Brian Kernighan's awk.  To this end,
       gawk  incorporates  the  following  user visible features which are not
       described in the AWK book, but are part of the Brian  Kernighan's  ver-
       sion of awk, and are in the POSIX standard.

       The  book  indicates that command line variable assignment happens when
       awk would otherwise open the argument as a file,  which  is  after  the
       BEGIN rule is executed.  However, in earlier implementations, when such
       an assignment appeared before any file names, the assignment would hap-
       pen before the BEGIN rule was run.  Applications came to depend on this
       "feature."  When awk was changed to match  its  documentation,  the  -v
       option  for  assigning  variables before program execution was added to
       accommodate applications that depended upon the  old  behavior.   (This
       feature  was  agreed  upon  by  both  the Bell Laboratories and the GNU

       When processing arguments, gawk uses the special option "--" to  signal
       the end of arguments.  In compatibility mode, it warns about but other-
       wise ignores undefined options.  In normal  operation,  such  arguments
       are passed on to the AWK program for it to process.

       The  AWK  book  does not define the return value of srand().  The POSIX
       standard has it return the seed it was using, to allow keeping track of
       random  number  sequences.   Therefore srand() in gawk also returns its
       current seed.

       Other features are: The use of multiple -f options (from MKS awk);  the
       ENVIRON array; the \a, and \v escape sequences (done originally in gawk
       and fed back into the Bell Laboratories  version);  the  tolower()  and
       toupper()  built-in functions (from the Bell Laboratories version); and
       the ISO C conversion specifications in printf (done first in  the  Bell
       Laboratories version).

       There  is  one feature of historical AWK implementations that gawk sup-
       ports: It is possible to call the length() built-in function  not  only
       with no argument, but even without parentheses!  Thus,

              a = length     # Holy Algol 60, Batman!

       is the same as either of

              a = length()
              a = length($0)

       Using  this  feature  is poor practice, and gawk issues a warning about
       its use if --lint is specified on the command line.

       Gawk has a too-large number of  extensions  to  POSIX  awk.   They  are
       described  in  this  section.  All the extensions described here can be
       disabled by invoking gawk with the --traditional or --posix options.

       The following features of gawk are not available in POSIX awk.

       o No path search is performed  for  files  named  via  the  -f  option.
         Therefore the AWKPATH environment variable is not special.

       o There is no facility for doing file inclusion (gawk's @include mecha-

       o There is no facility for dynamically adding new functions written  in
         C (gawk's @load mechanism).

       o The \x escape sequence.

       o The ability to continue lines after ?  and :.

       o Octal and hexadecimal constants in AWK programs.

         variables are not special.

       o The IGNORECASE variable and its side-effects are not available.

       o The FIELDWIDTHS variable and fixed-width field splitting.

       o The FPAT variable and field splitting based on field values.

       o The FUNCTAB, SYMTAB, and PROCINFO arrays are not available.

       o The use of RS as a regular expression.

       o The special file names available for I/O redirection are  not  recog-

       o The |& operator for creating coprocesses.

       o The BEGINFILE and ENDFILE special patterns are not available.

       o The  ability to split out individual characters using the null string
         as the value of FS, and as the third argument to split().

       o An optional fourth argument  to  split()  to  receive  the  separator

       o The optional second argument to the close() function.

       o The optional third argument to the match() function.

       o The ability to use positional specifiers with printf and sprintf().

       o The ability to pass an array to length().

       o The and(), asort(), asorti(), bindtextdomain(), compl(), dcgettext(),
         dcngettext(),  gensub(),  lshift(),   mktime(),   or(),   patsplit(),
         rshift(), strftime(), strtonum(), systime() and xor() functions.

       o Localizable strings.

       o Non-fatal I/O.

       o Retryable I/O.

       The  AWK book does not define the return value of the close() function.
       Gawk's close() returns the value from  fclose(3),  or  pclose(3),  when
       closing an output file or pipe, respectively.  It returns the process's
       exit status when closing an input pipe.  The return value is -1 if  the
       named file, pipe or coprocess was not opened with a redirection.

       When  gawk is invoked with the --traditional option, if the fs argument
       to the -F option is "t", then FS is set to  the  tab  character.   Note
       that  typing  gawk  -F\t ...  simply causes the shell to quote the "t,"
       and does not pass "\t" to the -F option.  Since this is a  rather  ugly
       special  case, it is not the default behavior.  This behavior also does
       not occur if --posix has been specified.  To really get a tab character
       as  the  field  separator, it is best to use single quotes: gawk -F'\t'

       The AWKPATH environment variable can be  used  to  provide  a  list  of
       directories that gawk searches when looking for files named via the -f,
       --file, -i and --include options, and the @include directive.   If  the
       initial  search  fails, the path is searched again after appending .awk
       to the filename.

       The AWKLIBPATH environment variable can be used to provide  a  list  of
       directories  that gawk searches when looking for files named via the -l
       and --load options.

       The GAWK_READ_TIMEOUT environment variable can be  used  to  specify  a
       timeout in milliseconds for reading input from a terminal, pipe or two-
       way communication including sockets.

       For connection to a remote host via socket, GAWK_SOCK_RETRIES  controls
       the  number  of  retries,  and GAWK_MSEC_SLEEP and the interval between
       retries.  The interval is in milliseconds. On systems that do not  sup-
       port  usleep(3),  the value is rounded up to an integral number of sec-

       If POSIXLY_CORRECT exists in the environment, then gawk behaves exactly
       as  if  --posix  had been specified on the command line.  If --lint has
       been specified, gawk issues a warning message to this effect.

       If the exit statement is used with a value, then gawk  exits  with  the
       numeric value given to it.

       Otherwise,  if there were no problems during execution, gawk exits with
       the value of the C constant EXIT_SUCCESS.  This is usually zero.

       If an error occurs, gawk  exits  with  the  value  of  the  C  constant
       EXIT_FAILURE.  This is usually one.

       If  gawk exits because of a fatal error, the exit status is 2.  On non-
       POSIX systems, this value may be mapped to EXIT_FAILURE.

       This man page documents gawk, version 4.2.

       The original version of UNIX awk was designed and implemented by Alfred
       Aho, Peter Weinberger, and Brian Kernighan of Bell Laboratories.  Brian
       Kernighan continues to maintain and enhance it.

       Paul Rubin and Jay Fenlason, of the  Free  Software  Foundation,  wrote
       gawk,  to be compatible with the original version of awk distributed in
       Seventh Edition UNIX.  John Woods contributed a number  of  bug  fixes.
       David  Trueman,  with contributions from Arnold Robbins, made gawk com-
       patible with the new version of UNIX awk.  Arnold Robbins is  the  cur-
       rent maintainer.

       See GAWK: Effective AWK Programming for a full list of the contributors
       to gawk and its documentation.

       See the README file in the gawk distribution for up-to-date information
       about maintainers and which ports are currently supported.

       If  you  find  a  bug  in  gawk,  please  send  electronic mail to bug-
       gawk@gnu.org.  Please include your operating system and  its  revision,
       the version of gawk (from gawk --version), which C compiler you used to
       compile it, and a test program and data that are as small  as  possible
       for reproducing the problem.

       Before  sending  a  bug report, please do the following things.  First,
       verify that you have the latest version of gawk.   Many  bugs  (usually
       subtle  ones)  are  fixed at each release, and if yours is out of date,
       the problem may already have been solved.  Second, please see  if  set-
       ting  the  environment  variable  LC_ALL  to  LC_ALL=C causes things to
       behave as you expect. If so, it's a locale issue, and may  or  may  not
       really  be a bug.  Finally, please read this man page and the reference
       manual carefully to be sure that what you think is  a  bug  really  is,
       instead of just a quirk in the language.

       Whatever  you do, do NOT post a bug report in comp.lang.awk.  While the
       gawk developers occasionally read this newsgroup, posting  bug  reports
       there  is  an  unreliable  way to report bugs.  Instead, please use the
       electronic mail addresses given above.  Really.

       If you're using a GNU/Linux or BSD-based system, you may wish to submit
       a  bug  report  to  the  vendor of your distribution.  That's fine, but
       please send a copy to the official email address as well, since there's
       no  guarantee  that  the bug report will be forwarded to the gawk main-

       The -F option is not necessary given the command line variable  assign-
       ment feature; it remains only for backwards compatibility.

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

       |Availability   | text/gawk        |
       |Stability      | Volatile         |
       egrep(1),   sed(1),   getpid(2),   getppid(2),  getpgrp(2),  getuid(2),
       geteuid(2),  getgid(2),  getegid(2),  getgroups(2),  printf(3),   strf-
       time(3), usleep(3)

       The  AWK Programming Language, Alfred V. Aho, Brian W. Kernighan, Peter
       J. Weinberger, Addison-Wesley, 1988.  ISBN 0-201-07981-X.

       GAWK: Effective AWK Programming, Edition 4.2,  shipped  with  the  gawk
       source.   The  current  version of this document is available online at

       The    GNU    gettext    documentation,     available     online     at

       Print and sort the login names of all users:

                      BEGIN              { FS = ":" }
                                         { print $1 | "sort" }

       Count lines in a file:

                                         { nlines++ }
                      END                { print nlines }

       Precede each line by its number in the file:

                      { print FNR, $0 }

       Concatenate and line number (a variation on a theme):

                      { print NR, $0 }

       Run an external command for particular lines of data:

                      tail -f access_log |
                      awk '/myhome.html/ { system("nmap " $1 ">> logdir/myhome.html") }'

       Brian  Kernighan provided valuable assistance during testing and debug-
       ging.  We thank him.

       Copyright (C) 1989, 1991, 1992, 1993, 1994,  1995,  1996,  1997,  1998,
       1999, 2001, 2002, 2003, 2004, 2005, 2007, 2009, 2010, 2011, 2012, 2013,
       2014, 2015, 2016, 2017, 2018 Free Software Foundation, Inc.

       Permission is granted to make and distribute verbatim  copies  of  this
       manual  page  provided  the copyright notice and this permission notice
       are preserved on all copies.

       Permission is granted to copy and distribute modified versions of  this
       manual  page  under  the conditions for verbatim copying, provided that
       the entire resulting derived work is distributed under the terms  of  a
       permission notice identical to this one.

       Permission  is granted to copy and distribute translations of this man-
       ual page into another language, under the above conditions for modified
       versions,  except that this permission notice may be stated in a trans-
       lation approved by the Foundation.

       This    software    was    built    from    source     available     at
       https://github.com/oracle/solaris-userland.    The  original  community
       source                was                downloaded                from

       Further information about this software can be found on the open source
       community website at https://www.gnu.org/software/gawk.

Free Software Foundation          Feb 15 2018                          GAWK(1)