Provided by: gawk_5.1.0-1build3_amd64 bug


       gawk - pattern scanning and processing language


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


       Gawk  is the GNU Project's implementation of the AWK programming 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 --include options), and values to be made available in  the  ARGC  and  ARGV
       pre-defined AWK variables.

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

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


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

       Gawk-specific options are typically used in long-option form.  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.


       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.   Files  read
              with -f are treated as if they begin with an implicit @namespace "awk" statement.

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

              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.

              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.

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

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

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

       -e program-text
       --source program-text
              Use  program-text  as  AWK  program  source  code.   This  option  allows  the easy
              intermixing of library functions (used via  the  -f  and  --include  options)  with
              source  code  entered  on the command line.  It is intended primarily for medium to
              large AWK programs used in shell scripts.  Each argument supplied via -e is treated
              as if it begins with an implicit @namespace "awk" statement.

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

              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.

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

       -l lib
       --load lib
              Load  a  gawk extension from the shared library lib.  This searches for the library
              using the AWKLIBPATH environment 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]
              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.)
              With an optional argument of no-ext, warnings about gawk extensions are disabled.

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

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

              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.

              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.  This  option  implies

              Enable  gawk's  default  optimizations  upon  the  internal  representation  of the
              program.  Currently, this just includes simple constant folding.  This option is on
              by default.

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

              This turns on compatibility mode, with the following additional 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 ^=.

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

              Disable gawk's default  optimizations  upon  the  internal  representation  of  the

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

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

              Print version information for this particular copy of gawk on the standard  output.
              This  is useful mainly for knowing if the current copy of gawk on your system is up
              to date with respect to whatever the  Free  Software  Foundation  is  distributing.
              This  is  also  useful  when  reporting bugs.  (Per the GNU Coding 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.


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

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

       Gawk first reads the program source from the program-file(s) if 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 --include

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

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

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

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

   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.


       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.

       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 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.

       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

       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,  including  leading  and  trailing whitespace.  Fields need not be
       referenced by constants:

              n = 5
              print $n

       prints the fifth field in the input record.

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

       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,
                   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 FS  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. When false, it does not.  The values
                   allowed for the --lint option may also be assigned  to  LINT,  with  the  same
                   effects.  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

       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.

                                        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 --load.

                                        "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 value of the getpgrp(2) system call.

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

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

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

                                        "os2"  OS/2.

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

                                        "vms"  OpenVMS or Vax/VMS.

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

                   PROCINFO["strftime"] The  default time format string for strftime().  Changing
                                        its value affects how strftime() formats time values when
                                        called with no arguments.

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

                   PROCINFO["version"]  The version of gawk.

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

                          The major version of the extension API.

                          The minor version of the extension API.

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

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

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

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

                          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:

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

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

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

                   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
                          in situations where a file descriptor has been configured to behave  in
                          a non-blocking fashion.

                          If  this  element exists in PROCINFO, then its value controls the order
                          in which array elements are 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

                               function cmp_func(i1, v1, i2, v2)

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

       ROUNDMODE   The rounding mode to use for arbitrary precision  arithmetic  on  numbers,  by
                   default "N" (IEEE-754 roundTiesToEven mode).  The accepted values are:

                   "A" or "a"
                          for  rounding away from zero.  These are only available if your version
                          of the GNU MPFR library supports rounding away from zero.

                   "D" or "d" for roundTowardNegative.

                   "N" or "n" for roundTiesToEven.

                   "U" or "u" for roundTowardPositive.

                   "Z" or "z" for roundTowardZero.

       RS          The input record separator, by default a newline.

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

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

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

       SUBSEP      The string used to separate multiple subscripts in array elements, by  default

       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,  nor  assign  to
                   elements with an index that is not a variable name.

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

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

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

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

       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

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

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

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

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

   Variable Typing And Conversion
       Variables  and fields may be (floating point) numbers, or strings, or both.  They may also
       be regular expressions. How the value of  a  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 (.).

       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.

       \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

       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.


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

              { print }

       which prints the entire record.

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

       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.

       AWK patterns may be one of the following:

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

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

       BEGINFILE and ENDFILE are additional special patterns whose actions  are  executed  before
       reading the first record of each command-line input file and after reading the last record
       of each file.  Inside the 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.

       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

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

       c          Matches the non-metacharacter c.

       \c         Matches the literal character c.

       .          Matches any character including newline.

       ^          Matches the beginning of a string.

       $          Matches the end of a string.

       [abc...]   A  character  list:  matches  any  of the characters abc....  You may include a
                  range of characters by separating them with a dash.  To include a literal  dash
                  in the list, put it first or last.

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

       [: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 e`.

       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.

       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

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

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

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

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

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

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

       (...)       Grouping

       $           Field reference.

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

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

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

       * / %       Multiplication, division, and modulus.

       + -         Addition and subtraction.

       space       String concatenation.

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

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

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

       in          Array membership.

       &&          Logical AND.

       ||          Logical OR.

       ?:          The C conditional expression.  This has the form expr1 ? expr2  :  expr3.   If
                   expr1  is  true,  the value of the 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
              delete array[index]
              delete array
              exit [ expression ]
              { statements }
              switch (expression) {
              case value|regex : statement
              [ default: statement ]

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

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

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

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

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

       getline var <file     Set var from the next record of file; set RT.

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

       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.  (The command
                             can also be a  socket.   See  the  subsection  Special  File  Names,

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

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

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

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

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

       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
              Append output to the file.

       print ... | command
              Write on a pipe.

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

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

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

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

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

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

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

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

       %f, %F  A floating point number of the form [-]ddd.dddddd.  If the 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

       %%      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

       -      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.

       #      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 the %s format,  it  specifies  the  maximum
              number of characters from the string that should be printed.

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

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

       -           The standard input.

       /dev/stdin  The standard input.

       /dev/stdout The standard output.

       /dev/stderr The standard error output.

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

       These are particularly useful for error messages.  For example:

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

       whereas you would otherwise have to use

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

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

              Files  for  a  TCP/IP connection on local port lport to remote host rhost on remote
              port rport.  Use a port of 0 to have the system pick a port.  Use /inet4  to  force
              an  IPv4  connection, and /inet6 to force an IPv6 connection.  Plain /inet uses the
              system default (most likely IPv4).  Usable only with the |& two-way I/O operator.

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

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

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

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

       exp(expr)     The exponential function.

       int(expr)     Truncate to integer.

       log(expr)     The natural logarithm function.

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

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

       sqrt(expr)    Return the square root of expr.

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

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

       asort(s [, d [, how] ]) Return the number of elements in the source  array  s.   Sort  the
                               contents  of s using gawk's normal rules for comparing values, and
                               replace the  indices  of  the  sorted  values  s  with  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

       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 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 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, seps).  Splitting
                               behaves identically  to  field  splitting,  described  above.   In
                               particular, if r is a single-character string, that string acts as
                               the separator, even if it  happens  to  be  a  regular  expression

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

       strtonum(str)           Examine  str,  and return its numeric value.  If str begins with a
                               leading 0, treat it as an 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.

       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  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 functions provide type related information about their arguments.

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

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

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

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

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


       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) ; ... }

       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

       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.


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


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


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

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

       always prints hello, world.  But,

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

       might print bonjour, monde in France.

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

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

                BEGIN { TEXTDOMAIN = "myprog" }

           This  allows  gawk  to  find the .gmo file associated with your 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

       5.  Provide appropriate translations, and build and install the corresponding .gmo files.

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


       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.

       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 developers and the GNU developers.)

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


       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.


       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.

       · 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

       · 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

       · 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().

       · 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' ....


       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

       For  connection  to  a  remote  host  via socket, GAWK_SOCK_RETRIES controls the number of
       retries,  and  GAWK_MSEC_SLEEP  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 exactly as if --posix  had
       been  specified  on the command line.  If --lint has been specified, gawk issues a warning
       message to this effect.


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

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

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

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


       This man page documents gawk, version 5.1.


       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

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

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


       If you find a bug in gawk,  please  send  electronic  mail  to   Please
       include your operating system and its 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 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.   Similarly,  do  NOT  use  a web forum (such as Stack Overflow) for reporting bugs.
       Instead, please use the electronic mail addresses given above.  Really.

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


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


       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 5.1, shipped with the gawk source.   The  current
       version of this document is available online at

       The GNU gettext documentation, available online at


       Print and sort the login names of all users:

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

       Count lines in a file:

                 { nlines++ }
            END  { print nlines }

       Precede each line by its number in the file:

            { print FNR, $0 }

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

            { print NR, $0 }

       Run an external command for particular lines of data:

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


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


       Copyright  © 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2001, 2002, 2003,
       2004, 2005, 2007, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019,  2020,
       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.