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 GAWK(1)                  Free Software Foundation                   GAWK(1)
 Utility Commands                                           Utility Commands

                                 Feb 15 2018



 NAME
      gawk - pattern scanning and processing language

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

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

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

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

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

 OPTION FORMAT
      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.
      Arguments 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 abbreviation remains unique.

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

 OPTIONS



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 GAWK(1)                  Free Software Foundation                   GAWK(1)
 Utility Commands                                           Utility Commands

                                 Feb 15 2018



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

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

      -F fs
      --field-separator fs
           Use fs for the input field separator (the value of the FS
           predefined 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.

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

























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                                 Feb 15 2018



      -c
      --traditional
           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
           information.

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

      -d[file]
      --dump-variables[=file]
           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.)

      -D[file]
      --debug[=file]
           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 commands
           for the debugger to execute non-interactively.

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

      -E file
      --exec file
           Similar to -f, however, this is option is the last one processed.
           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.





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                                 Feb 15 2018



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

      -h
      --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
           eliminated), and the code does not constitute the main program
           source.

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

      -L [value]
      --lint[=value]
           Provide warnings about constructs that are dubious or non-
           portable 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
           warnings about things that are actually invalid are issued. (This
           is not fully implemented yet.)

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

      -n



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

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

      -o[file]
      --pretty-print[=file]
           Output a pretty printed version of the program to file.  If no
           file is provided, gawk uses a file named awkprof.out in the
           current directory.  Implies --no-optimize.

      -O
      --optimize
           Enable gawk's default optimizations upon the internal
           representation of the program.  Currently, this includes simple
           constant-folding, and tail call elimination for recursive
           functions.  This option is on by default.

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

      -P
      --posix
           This turns on compatibility mode, with the following additional
           restrictions:

           + \x escape sequences are not recognized.

           + You cannot continue lines after ? and :.

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

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

      -r



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 GAWK(1)                  Free Software Foundation                   GAWK(1)
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                                 Feb 15 2018



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

      -s
      --no-optimize
           Disable gawk's default optimizations upon the internal
           representation of the program.

      -S
      --sandbox
           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.

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

      -V
      --version
           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 Standards,
           these options cause an immediate, successful exit.)

      --   Signal the end of options. This is useful to allow further
           arguments to the AWK program itself to start with a ``-''.  This
           provides 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.



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 GAWK(1)                  Free Software Foundation                   GAWK(1)
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                                 Feb 15 2018



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

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

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

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

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

      The environment variable AWKPATH specifies a search path to use when
      finding source files named with the -f and -i options.  If this
      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 ``/''
      character, no path search is performed.

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

      Gawk executes AWK programs in the following order.  First, all
      variable assignments specified via the -v option are performed.  Next,
      gawk compiles 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



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 GAWK(1)                  Free Software Foundation                   GAWK(1)
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      line variable assignment is most useful for dynamically assigning
      values to the variables AWK uses to control how input is broken into
      fields and records.  It is also useful for controlling state if
      multiple passes are needed over a single data file.

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

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

      For each record in the input, gawk tests to see if it matches any
      pattern 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
      produces a warning, but is otherwise skipped.  If either of the
      --posix or --traditional options is given, then gawk reverts to
      treating directories on the command line as a fatal error.

 VARIABLES, RECORDS AND FIELDS
      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 dimensional 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.

    Records
      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 compatibility mode, only the first character of its string value is
      used for separating records.  If RS is set to the null string, then



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 GAWK(1)                  Free Software Foundation                   GAWK(1)
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                                 Feb 15 2018



      records are separated by empty lines.  When RS is set to the null
      string, the newline character always acts as a field separator, in
      addition to whatever value FS may have.

    Fields
      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.  Otherwise, 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
      numbers, 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 characters to skip before the field starts.  The value of FS
      is ignored.  Assigning a new value to FS or FPAT overrides the use of
      FIELDWIDTHS.

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

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

           n = 5
           print $n

      prints the fifth field in the input record.

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

      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
      recomputed, 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



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 GAWK(1)                  Free Software Foundation                   GAWK(1)
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                                 Feb 15 2018



      lost, and the value of $0 to be recomputed, with the fields being
      separated by the value of OFS.

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

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

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

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

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

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

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

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

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

      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,



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                                 Feb 15 2018



                  PROCINFO["errno"] will be zero.

      FIELDWIDTHS A whitespace-separated list of field widths.  When set,
                  gawk parses the input into fields of fixed width, instead
                  of using the value of the FS variable as the field
                  separator.  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
                  specified on the command line, the value of FILENAME is
                  ``-''.  However, FILENAME is undefined inside the BEGIN
                  rule (unless set by getline).

      FNR         The input record number in the current input file.

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

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

      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 gensub(), gsub(), index(), match(), patsplit(),
                  split(), and sub() built-in functions all ignore case when
                  doing regular expression operations.  NOTE: Array
                  subscripting is not affected.  However, the asort() and
                  asorti() functions are affected.
                  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-sensitive.

      LINT        Provides dynamic control of the --lint option from within
                  an AWK program.  When true, gawk prints lint warnings.



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                  When false, it does not.  When assigned the string value
                  "fatal", lint warnings become fatal errors, exactly like
                  --lint=fatal.  Any other true value just prints warnings.

      NF          The number of fields in the current input record.

      NR          The total number of input records seen so far.

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

      OFS         The output field separator, a space by default.

      ORS         The output record separator, by default a newline.

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

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

                  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
                                       call.

                  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
                                       call.

                  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
                                       call.




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                  PROCINFO["identifiers"]
                                       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
                                       program; they are not updated while
                                       the program runs.  For each
                                       identifier, the value of the element
                                       is one of the following:

                                       "array"     The identifier is an
                                                   array.

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

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

                                       "scalar"    The identifier is a
                                                   scalar.

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

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

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

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

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

                  PROCINFO["strftime"] The default time format string for
                                       strftime().

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

                  PROCINFO["version"]  the version of gawk.




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

                  PROCINFO["api_major"]
                       The major version of the extension API.

                  PROCINFO["api_minor"]
                       The minor version of the extension API.

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

                  PROCINFO["gmp_version"]
                       The version of the GNU MP library used for arbitrary
                       precision number support in gawk.

                  PROCINFO["mpfr_version"]
                       The version of the GNU MPFR library used for
                       arbitrary precision number support in gawk.

                  PROCINFO["prec_max"]
                       The maximum precision supported by the GNU MPFR
                       library for arbitrary precision floating-point
                       numbers.

                  PROCINFO["prec_min"]
                       The minimum precision allowed by the GNU MPFR library
                       for arbitrary precision floating-point numbers.

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

                  PROCINFO["NONFATAL"]
                       If this exists, then I/O errors for all redirections
                       become nonfatal.

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

                  PROCINFO["command", "pty"]
                       Use a pseudo-tty for two-way communication with
                       command 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
                       timeout.




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

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

                            function cmp_func(i1, v1, i2, v2)

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

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

      RS          The input record separator, by default a newline.

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

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



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

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

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

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

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

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

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

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

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




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      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
      subarray in order to use it where gawk expects an array (such as in
      the second argument to split()).  You can do this by creating an
      element in the subarray and then deleting it with the delete
      statement.

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

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

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

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



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

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

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

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

      \\   A literal backslash.

      \a   The ``alert'' character; usually the ASCII BEL character.

      \b   Backspace.

      \f   Form-feed.

      \n   Newline.

      \r   Carriage return.

      \t   Horizontal tab.

      \v   Vertical tab.

      \xhex digits
           The character represented by the string of hexadecimal digits
           following the \x.  Up to two following hexadecimal digits are
           considered 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.




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      \c   The literal character c.

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

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

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

      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 regular expression type.

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

           { print }

      which prints the entire record.

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

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

    Patterns
      AWK patterns may be one of the following:

           BEGIN



                                   - 19 -      Formatted:  December 16, 2018






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           END
           BEGINFILE
           ENDFILE
           /regular expression/
           relational expression
           pattern && 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
      combined with other patterns in pattern expressions.  BEGIN and END
      patterns cannot have missing action parts.

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

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

      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,
      otherwise it is the third.  Only one of the second and third patterns
      is evaluated.




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      The pattern1, pattern2 form of an expression is called a range
      pattern.  It matches all input records starting with a record that
      matches pattern1, 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.

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

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

      \y         Matches the empty string at either the beginning or the end



                                   - 21 -      Formatted:  December 16, 2018






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                 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
                 underscore).

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

      \`         Matches the empty string at the beginning of a buffer
                 (string).

      \'         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
      characters 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
      keyword 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.)



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      [:lower:]  Lowercase alphabetic characters.

      [:print:]  Printable characters (characters that are not control
                 characters.)

      [:punct:]  Punctuation characters (characters that are not letter,
                 digits, 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
      characters, 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
      collating, or sorting, purposes.  (E.g., in French, a plain ``e'' and
      a grave-accented ```'' are equivalent.)

      Collating Symbols
           A collating symbol is a multi-character collating element
           enclosed in [. and .].  For example, if ch is a collating
           element, 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
           expression 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
      currently only recognize POSIX character classes; they do not
      recognize collating symbols or equivalence classes.



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

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

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

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

      --traditional
           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.

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

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

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

      (...)       Grouping

      $           Field reference.

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

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

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

      * / %       Multiplication, division, and modulus.




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      + -         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
                  expression is expr2, otherwise it is expr3.  Only one of
                  expr2 and expr3 is evaluated.

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

    Control Statements
      The control statements are as follows:

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



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

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

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

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

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

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

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

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

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

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

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

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




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      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,
                            below.

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

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

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

      Additional output redirections are allowed for print and printf.

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

      print ... | command
           Writes on a pipe.

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

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

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

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



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      %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
              system 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
              nonsignificant 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
      letter:

      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 original
           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 modifier.




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

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

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

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

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

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

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

      -           The standard input.

      /dev/stdin  The standard input.



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      /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
      operator for creating TCP/IP network connections:

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

      /inet/udp/lport/rhost/rport
      /inet4/udp/lport/rhost/rport
      /inet6/udp/lport/rhost/rport
           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.




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      sqrt(expr)    Return the square root of expr.

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

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

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

      asorti(s [, d [, how] ])
                              Return the number of elements in the source
                              array s.  The behavior is the same as that of
                              asort(), except that the array indices are
                              used for sorting, not the array values.  When
                              done, the array is indexed numerically, and
                              the values 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
                              beginning 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 supplied, 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 subexpression.  The sequence \0
                              represents the entire matched text, as does



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                              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
                              expression r in the string t, substitute the
                              string s, and return the number of
                              substitutions.  If t is not supplied, use $0.
                              An & in the replacement text is replaced with
                              the text that was actually matched.  Use \& to
                              get a literal &.  (This must be typed as
                              "\\&"; see GAWK: Effective AWK Programming for
                              a fuller discussion of the rules for
                              ampersands and backslashes in the replacement
                              text of sub(), gsub(), and gensub().)

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

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

      match(s, r [, a])       Return the position in s where the regular
                              expression r occurs, or zero if r is not
                              present, and set the values of RSTART and
                              RLENGTH.  Note that the argument order is the
                              same as for the ~ operator: str ~ re.  If
                              array a is provided, a is cleared and then
                              elements 1 through n are filled with the
                              portions of s that match the corresponding
                              parenthesized 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 matching
                              substring.

      patsplit(s, a [, r [, seps] ])
                              Split the string s into the array a and the
                              separators array seps on the regular
                              expression r, and return the number of fields.
                              Element values are the portions of s that



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                              matched r.  The value of seps[i] is the
                              possibly null separator that appeared after
                              a[i].  The value of seps[0] is the possibly
                              null leading separator.  If r is omitted, FPAT
                              is used instead.  The arrays a and seps are
                              cleared first.  Splitting behaves identically
                              to field splitting with FPAT, described above.

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

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

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

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

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

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

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



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      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
      functions 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
                respectively 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
                preceding 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 negative (the default), mktime() attempts to determine
                whether daylight saving time is in effect for the specified
                time.  If datespec does not contain enough elements or if
                the resulting time is out of range, mktime() returns -1.

      strftime([format [, timestamp[, utc-flag]]])
                Format timestamp according to the specification in format.
                If utc-flag is present and is non-zero or non-null, the
                result is in UTC, otherwise the result is in local time.
                The timestamp should be of the same form as returned by
                systime().  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
                available 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



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      integers, doing the operation, and then converting the result back to
      floating point.

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

      The functions are:

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

      compl(val)          Return the bitwise complement of val.

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

      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
                          bits.

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

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

      isarray(x)
           Return true if x is an array, false otherwise.

      You can tell the type of any variable or array element with the
      following function:

      typeof(x)
           Return a string indicating the type of x.  The string will be one
           of "array", "number", "regexp", "string", "strnum", 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''
           locations (e.g., during testing).  It returns the directory where
           domain is ``bound.''



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           The default domain is the value of TEXTDOMAIN.  If directory is
           the null string (""), then bindtextdomain() returns the current
           binding for the given domain.

      dcgettext(string [, domain [, category]])
           Return the translation of string in text domain domain for locale
           category category.  The default value for domain is the current
           value of TEXTDOMAIN.  The default value for category is
           "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.

      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.

 USER-DEFINED FUNCTIONS
      Functions in AWK are defined as follows:

           function name(parameter list) { statements }

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

      Since functions were not originally part of the AWK language, the
      provision 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) ; ... }




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

      Functions may call each other and may be recursive.  Function
      parameters 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
      ``falling 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
      variable.  Then use the variable as if it were the name of a function,
      prefixed 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
      functions 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
      deprecated.

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

 SIGNALS
      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.



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 INTERNATIONALIZATION
      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
          program.  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
          underscores.

      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
          corresponding .gmo files.

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

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




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

      When processing arguments, gawk uses the special option ``--'' to
      signal the end of arguments.  In compatibility mode, it warns about
      but otherwise 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).

 HISTORICAL FEATURES
      There is one feature of historical AWK implementations that gawk
      supports: 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.

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

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



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

      + There is no facility for doing file inclusion (gawk's @include
        mechanism).

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

      + The \x escape sequence.

      + The ability to continue lines after ? and :.

      + Octal and hexadecimal constants in AWK programs.

      + The ARGIND, BINMODE, ERRNO, LINT, PREC, ROUNDMODE, RT and TEXTDOMAIN
        variables are not special.

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

      + The FIELDWIDTHS variable and fixed-width field splitting.

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

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

      + The use of RS as a regular expression.

      + The special file names available for I/O redirection are not
        recognized.

      + The |& operator for creating coprocesses.

      + The BEGINFILE and ENDFILE special patterns are not available.

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

      + An optional fourth argument to split() to receive the separator
        texts.

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

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

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

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




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

      + Localizable strings.

      + Non-fatal I/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' ....

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

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

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

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

      If POSIXLY_CORRECT exists in the environment, then gawk behaves



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

 EXIT STATUS
      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.

 VERSION INFORMATION
      This man page documents gawk, version 4.2.

 AUTHORS
      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
      compatible with the new version of UNIX awk.  Arnold Robbins is the
      current 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.

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

      Before sending a bug report, please do the following things.  First,
      verify that you have the latest version of gawk.  Many bugs (usually
      subtle ones) are fixed at each release, and if yours is out of date,
      the problem may already have been solved.  Second, please see if



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      setting the environment variable LC_ALL to LC_ALL=C causes things to
      behave as you expect. If so, it's a locale issue, and may or may not
      really be a bug.  Finally, please read this man page and the reference
      manual carefully to be sure that what you think is a bug really is,
      instead of just a quirk in the language.

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

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

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

 SEE ALSO
      egrep(1), sed(1), getpid(2), getppid(2), getpgrp(2), getuid(2),
      geteuid(2), getgid(2), getegid(2), getgroups(2), printf(3),
      strftime(3), usleep(3)

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

      GAWK: Effective AWK Programming, Edition 4.2, shipped with the gawk
      source.  The current version of this document is available online at
      https://www.gnu.org/software/gawk/manual.

      The GNU gettext documentation, available online at
      https://www.gnu.org/software/gettext.

 EXAMPLES
      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:




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           { 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") }'

 ACKNOWLEDGEMENTS
      Brian Kernighan provided valuable assistance during testing and
      debugging.  We thank him.

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

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

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

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



















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