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 --include 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 and --include options.  The debugger is documented in
       GAWK: Effective 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.  Files read with -f are treated as
              if they begin with an implicit @namespace "awk" statement.

       -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 op-
              tion 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
              --include options) with source code entered on the command line.
              It is intended primarily for medium to large AWK  programs  used
              in  shell  scripts.  Each argument supplied via -e is treated as
              if it begins with an implicit @namespace "awk" statement.

       -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 in-
              formation 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
              source.   Files read with --include are treated as if they begin
              with an implicit @namespace "awk" statement.

       -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.)  With an optional argument of no-
              ext, warnings about gawk extensions are disabled.

              Force arbitrary precision arithmetic on numbers. This option has
              no  effect  if  gawk is not compiled to use the GNU MPFR and GMP
              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 de-
              fault is to follow traditional behavior and use a period as  the
              decimal point, even in locales where the period is not the deci-
              mal point character.  This option overrides the  default  behav-
              ior,  without  the  full draconian strictness of the --posix op-

              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.  This option implies --no-optimize.

              Enable gawk's default optimizations upon the internal  represen-
              tation  of  the  program.   Currently, this just includes simple
              constant folding.  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.  This
              option 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 together 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"
              @namespace "name"
              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 to-
       gether.  This is useful for building libraries of AWK functions,  with-
       out  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 --include option.

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

       The environment variable AWKPATH specifies a search path  to  use  when
       finding  source files named with the -f and --include options.  If this
       variable 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 --load 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  as-
       sociated  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.  As-
       signing 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, including leading and  trailing
       whitespace.  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  op-
                   tions 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 el-
                   ement  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 en-
                   vironment seen by programs which gawk spawns via  redirect-
                   ion  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["er-
                   rno"] 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 (un-
                   less 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 FS as the field separator.  See Fields,

       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 af-
                   fected.  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 "fa-
                   tal", 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 el-
                   ements.  The following elements are guaranteed to be avail-

                   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 ar-

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

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

                                        "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 value  of  the  getpgrp(2)  system

                   PROCINFO["pid"]      The  value  of  the  getpid(2)  system

                   PROCINFO["platform"] A string indicating the  platform  for
                                        which  gawk  was  compiled.  It is one

                                        "djgpp", "mingw"
                                               Microsoft Windows, using either
                                               DJGPP, or MinGW, respectively.

                                        "os2"  OS/2.

                                               GNU/Linux,  Cygwin,  Mac  OS X,
                                               and legacy Unix systems.

                                        "vms"  OpenVMS or Vax/VMS.

                   PROCINFO["ppid"]     The value  of  the  getppid(2)  system

                   PROCINFO["strftime"] The  default  time  format  string for
                                        strftime().  Changing  its  value  af-
                                        fects how strftime() formats time val-
                                        ues when called with no arguments.

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

                   PROCINFO["version"]  The version of gawk.

                   The  following  elements are present if loading dynamic ex-
                   tensions 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 GMP library used for arbi-
                          trary 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 li-
                          brary for arbitrary  precision  floating-point  num-

                          The  minimum  precision  allowed by the GNU MPFR li-
                          brary 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["name", "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  ex-
                          ists,  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  in  situations where a file de-
                          scriptor has been configured to  behave  in  a  non-
                          blocking fashion.

                          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:

                   "A" or "a"
                          for  rounding away from zero.  These are only avail-
                          able if your version of the GNU  MPFR  library  sup-
                          ports rounding away from zero.

                   "D" or "d" for roundTowardNegative.

                   "N" or "n" for roundTiesToEven.

                   "U" or "u" for roundTowardPositive.

                   "Z" or "z" for roundTowardZero.

       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 string used to separate multiple  subscripts  in  array
                   elements, by default "\034".

       SYMTAB      An  array  whose indices are the names of all currently de-
                   fined global variables and arrays in the program.  The  ar-
                   ray  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, nor assign to elements with an index
                   that is not a variable name.

       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  ar-
       rays.  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.

       Gawk provides a simple namespace facility to help work around the  fact
       that all variables in AWK are global.

       A  qualified name consists of a two simple identifiers joined by a dou-
       ble colon (::).  The left-hand identifier represents the namespace  and
       the  right-hand identifier is the variable within it.  All simple (non-
       qualified) names are considered to be in the ``current'' namespace; the
       default  namespace  is  awk.   However,  simple  identifiers consisting
       solely of uppercase letters are forced into the awk namespace, even  if
       the current namespace is different.

       You change the current namespace with an @namespace "name" directive.

       The standard predefined builtin function names may not be used as name-
       space names.  The names of additional functions provided by gawk may be
       used  as  namespace names or as simple identifiers in other namespaces.
       For more details, see GAWK: Effective AWK Programming.

   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 ex-
       pression,  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  nu-
       meric  value of the variable as the argument.  However, even though all
       numbers in AWK are floating-point, integral values are always converted
       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 nu-
       meric 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  ex-
       pression constants.  Thus, /a\52b/ is equivalent to /a\*b/.

   Regexp Constants
       A  regular expression constant is a sequence of characters enclosed be-
       tween 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  constants
       may  be  assigned  to scalars (variables, array elements) and passed to
       user-defined functions. Variables that have been so assigned have regu-
       lar 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.  However, a "\" after a # is not

       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 actions 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 ex-
       pressions are the same as those in egrep(1), and are summarized below.

       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
                  dash.   To  include a literal dash in the list, put it first
                  or last.

       [^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 re-
                  peated 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 en-
              closed 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 ex-
       pression 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 de-
              scribed 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 in-
       put/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  as-
                   signment 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 op-
                   erator-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 the next input record;  set  NF,  NR,
                             FNR, RT.

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

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

       getline var <file     Set var from the next record of file; set 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 ei-
                             ther into $0 or var, as above,  and  RT.   Copro-
                             cesses  are  a  gawk extension.  (The command can
                             also be a socket.   See  the  subsection  Special
                             File Names, below.)

       next                  Stop  processing  the current input record.  Read
                             the next input record and start  processing  over
                             with  the first pattern in the AWK program.  Upon
                             reaching the end of the input data,  execute  any
                             END rule(s).

       nextfile              Stop processing the current input file.  The next
                             input record read comes from the next input file.
                             Update  FILENAME  and ARGIND, reset FNR to 1, and
                             start processing over with the first  pattern  in
                             the  AWK  program.   Upon reaching the end of the
                             input data, execute 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, be-

       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
              Append output to the file.

       print ... | command
              Write on a pipe.

       print ... |& command
              Send 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 re-
       turned 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:

       %a, %A  A floating point number of the form [-]0xh.hhhhp+-dd (C99 hexa-
               decimal floating point format).  For %A, uppercase letters  are
               used instead of lowercase ones.

       %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  al-
              ways  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 the %s
              format, 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 in-
       ternally.  These filenames allow access to open file descriptors inher-
       ited  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

       -           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 de-
              fault (most likely IPv4).  Usable only with the |&  two-way  I/O

              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 ar-
                               ray  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 in-
                               dices  of the source array s unchanged. The op-
                               tional 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  de-
                               scribed in PROCINFO["sorted_in"].

       asorti(s [, d [, how] ])
                               Return the number of elements in the source ar-
                               ray 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 en-
                               tire 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  re-
                               placement  text  is replaced with the text that
                               was actually matched.  Use \& to get a  literal
                               &.  (This must be typed as "\\&"; see GAWK: Ef-
                               fective AWK Programming for a fuller discussion
                               of  the rules for ampersands and backslashes in
                               the replacement text of sub(), gsub(), and gen-

       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  ex-
                               pression 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 subexpression in r.
                               The zero'th element of a contains  the  portion
                               of  s  matched by the entire regular expression
                               r.   Subscripts   a[n,   "start"],   and   a[n,
                               "length"]  provide  the  starting  index in the
                               string and length respectively, of each  match-
                               ing 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 ar-
                               rays  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 ar-
                               ray element seps[n],  where  n  is  the  return
                               value  of  split(s, a, r, seps).  Splitting be-
                               haves identically to field splitting, described
                               above.  In particular, if r is a single-charac-
                               ter string, that string acts as the  separator,
                               even  if  it happens to be a regular expression

       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 oc-
                               tal number.  If str begins with a leading 0x or
                               0X, treat it as a hexadecimal  number.   Other-
                               wise, 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-al-
                               phabetic 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-al-
                               phabetic 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  re-
                 sult  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  fa-
       tal 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 functions provide type related  information  about  their

       isarray(x) Return  true  if x is an array, false otherwise.  This func-
                  tion is mainly for use with the elements of multidimensional
                  arrays and with function parameters.

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

   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  lo-
              cale  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  ei-
       ther  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 functions written in C or C++ to  the  run-
       ning  gawk  interpreter with the @load statement.  The full details are
       beyond the scope of this manual page; see GAWK: Effective AWK  Program-

       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 de-
       scribed  in the AWK book, but are part of the Brian Kernighan's version
       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 BE-
       GIN 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 op-
       tion for assigning variables before program execution was added to  ac-
       commodate applications that depended upon the old behavior.  (This fea-
       ture was agreed upon by both the Bell Laboratories developers  and  the
       GNU developers.)

       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 de-
       scribed in this section.  All the extensions described here can be dis-
       abled 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 di-
       rectories 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  the  interval  between  re-
       tries.  The interval is in milliseconds. On systems that do not support
       usleep(3), the value is rounded up to an integral number of seconds.

       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 5.0.

       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  Please include your operating system and  its  revi-
       sion,  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 be-
       have as you expect. If so, it's a locale issue, and may or may not  re-
       ally  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, in-
       stead 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.  Similarly, do NOT use a web
       forum (such as Stack Overflow) for reporting 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.

       egrep(1), sed(1), getpid(2),  getppid(2),  getpgrp(2),  getuid(2),  ge-
       teuid(2),  getgid(2), getegid(2), getgroups(2), printf(3), strftime(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 5.0, 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, 2019, 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.

Free Software Foundation          May 22 2019                          GAWK(1)
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