Provided by: gawk_4.0.1+dfsg-2.1ubuntu2_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 ...

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

       dgawk [ POSIX or GNU style options ] -f program-file [ -- ] 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  UNIX
       awk and a number of GNU-specific extensions.

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

       Pgawk is the profiling version of gawk.  It is identical in every way to gawk, except that
       programs run more slowly, and it automatically produces an execution profile in  the  file
       awkprof.out when done.  See the --profile option, below.

       Dgawk is an awk debugger. Instead of running the program directly, it loads the AWK source
       code and then prompts for debugging commands.  Unlike gawk and pgawk, dgawk only processes
       AWK  program  source  provided  with  the  -f option.  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,  each  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.

       -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 block 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 UNIX
              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.)

       -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 --file options)  with  source
              code entered on the command line.  It is intended primarily for medium to large AWK
              programs used in shell scripts.

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

              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.)

       -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.)

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

              This forces 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.

              Enable  optimizations  upon the internal representation of the program.  Currently,
              this includes just simple  constant-folding.  The  gawk  maintainer  hopes  to  add
              additional optimizations over time.

              Send profiling data to prof_file.  The default is awkprof.out.  When run with gawk,
              the profile is just a “pretty printed” version  of  the  program.   When  run  with
              pgawk,  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 turns on compatibility mode, with the following additional restrictions:

              · \x escape sequences are not recognized.

              · Only space and tab act as field separators when FS is  set  to  a  single  space,
                newline does not.

              · 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 ^=.

              · The fflush() function is not available.

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

       --command file
              Dgawk only.  Read stored debugger commands from file.

              Runs  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.


       An  AWK  program consists of a sequence of pattern-action statements and optional function

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

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

       In addition, lines beginning with @include may be used to include other source files  into
       your program, making library use even easier.

       The  environment variable AWKPATH specifies a search path to use when finding source files
       named with the -f  option.   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.

       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 block(s) (if any), and then
       proceeds to read each file named in the ARGV array (up to ARGV[ARGC]).  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  block(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, the associated action is executed.
       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 block(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.   AWK  also  has  one  dimensional  arrays;  arrays  with multiple dimensions may be
       simulated.  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  blank  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.   (But  see the section POSIX COMPATIBILITY, below).  NOTE: The value of
       IGNORECASE (see below) also affects how fields are split when FS is a regular  expression,
       and how records are separated when RS is a regular expression.

       If  the  FIELDWIDTHS  variable  is set to a space separated list of numbers, each field is
       expected to have fixed width, and gawk splits up the record using  the  specified  widths.
       The  value  of  FS  is  ignored.  Assigning a new value to FS or FPAT overrides the use of

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

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

              n = 5
              print $n

       prints the fifth field in the input record.

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

       References to non-existent  fields  (i.e.  fields  after  $NF)  produce  the  null-string.
       However,  assigning to a non-existent field (e.g., $(NF+2) = 5) increases the value of NF,
       creates any intervening fields with the null string as their value, 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).  Changing  this  array
                   does  not  affect  the  environment  seen  by  programs  which gawk spawns via
                   redirection or the system() function.

       ERRNO       If a system error occurs either doing a redirection for getline, during a read
                   for  getline, or during a close(), then ERRNO will contain a string describing
                   the error.  The value is subject to translation in non-English locales.

       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.  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 block (unless set by getline).

       FNR         The input record number in the current input file.

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

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

       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.  When assigned
                   the string value "fatal", lint warnings  become  fatal  errors,  exactly  like
                   --lint=fatal.  Any other true value just prints warnings.

       NF          The number of fields in the current input record.

       NR          The total number of input records seen so far.

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

       OFS         The output field separator, a space by default.

       ORS         The output record separator, by default a newline.

       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["egid"]    the value of the getegid(2) system call.

                                       The default time format string for strftime().

                   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,  or  "FIELDWIDTHS"
                                       if field splitting with FIELDWIDTHS is in effect.

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

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

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

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

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

                                       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 of any
                                       comparison function defined as follows:

                          function cmp_func(i1, v1, i2, v2)

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

                          the version of gawk.

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

       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

       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

   Variable Typing And Conversion
       Variables  and fields may be (floating point) numbers, or strings, or both.  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 0 to it; to force it to be treated as a
       string, concatenate it with the null 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 command line 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.

       Uninitialized  variables  have  the  numeric value 0 and the string value "" (the null, or
       empty, string).

   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.  As
            in ANSI C, all following  hexadecimal  digits  are  considered  part  of  the  escape
            sequence.    (This  feature  should  tell  us  something  about  language  design  by
            committee.)  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.

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

       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/.


       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  is  executed
       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.  Blank 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

       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 block.  They are executed before  any  of  the  input  is  read.
       Similarly, all the END blocks are merged, and executed when all the input is exhausted (or
       when an exit statement is executed).  BEGIN and END patterns cannot be combined with other
       patterns in pattern expressions.  BEGIN and END patterns cannot have missing action parts.

       BEGINFILE  and  ENDFILE  are  additional special patterns whose bodies are executed before
       reading the first record of each command line input file and after reading the last record
       of  each  file.  Inside the BEGINFILE rule, the value of ERRNO will be the empty string if
       the file could be 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...]   character list, matches any of the characters abc....

       [^abc...]  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  below)  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 provide 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 was intended.

       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 co-process.  The optional  how  should  only  be
                             used  when  closing  one  end of a two-way pipe to a co-process.  It
                             must be a string value, either "to" or "from".

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

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

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

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

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

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

       next                  Stop processing the current input record.  The next input record  is
                             read  and  processing  starts over with the first pattern in the AWK
                             program.  If the end of the input data is reached, the END block(s),
                             if any, are executed.

       nextfile              Stop  processing the current input file.  The next input record read
                             comes from the next input file.  FILENAME and  ARGIND  are  updated,
                             FNR is reset to 1, and processing starts over with the first pattern
                             in the AWK program. If the end of the input data is reached, the END
                             block(s), if any, are executed.

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

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

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

       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.)

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

       Additional output redirections are allowed for print and printf.

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

       print ... | command
              Writes on a pipe.

       print ... |& command
              Sends data to a co-process or socket.  (See also the subsection Special File Names,

       The getline command returns 1 on success, 0 on end of file, and -1 on an error.   Upon  an
       error, ERRNO contains a string describing the problem.

       NOTE:  Failure in opening a two-way socket will result in a non-fatal error being returned
       to the calling function. If using a pipe, co-process, 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 co-processes when they return

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

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

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

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

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

       width  The field should be padded to this  width.   The  field  is  normally  padded  with
              spaces.  If the 0 flag has been used, it is padded with zeroes.

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

       The dynamic width and prec capabilities of the ANSI 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:

       /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 |& co-process 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).

              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 0 and 1, such that 0 ≤ N < 1.

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

       sqrt(expr)    The square root function.

       srand([expr]) Use  expr  as  the  new seed for the random number generator.  If no expr is
                     provided, use the time of day.  The return value is 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, then 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 in asort() above.

       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 &'s 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 0 if t is not
                               present.  (This implies that character indices start at one.)

       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
                               0 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 0'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 separator that appeared in front of a[i+1].  If r
                               is omitted, FPAT is used instead.   The  arrays  a  and  seps  are
                               cleared  first.   Splitting behaves identically to field splitting
                               with FPAT, described above.

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

       sprintf(fmt, expr-list) Prints expr-list according  to  fmt,  and  returns  the  resulting

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

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

       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.

                 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.  The time is
                 assumed  to  be in the local timezone.  If the 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 ANSI 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.  The functions are:

       and(v1, v2)         Return the bitwise AND of the values provided by v1 and v2.

       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 by v1 and v2.

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

       xor(v1, v2)         Return the bitwise XOR of the values provided by v1 and v2.

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

              Return true if x is an array, false otherwise.

   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 .mo 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 are executed 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

       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.


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

       extension(object, function)
               Dynamically link the shared object file named by object, and  invoke  function  in
               that object, to perform initialization.  These should both be provided as strings.
               Return the value returned by function.

       Using this feature at the C level is not pretty, but it is unlikely to go away. Additional
       mechanisms may be added at some point.


       pgawk 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 pgawk 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 .mo file associated with your program.   Without  this  step,
       gawk  uses  the  messages text domain, which likely does not contain translations for your

       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 .po file for your program.

       5.  Provide appropriate translations, and build and install the corresponding .mo 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  UNIX  awk.  To this end, gawk incorporates the following user visible
       features which are not described in the AWK book, but are part of  the  Bell  Laboratories
       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  block  is  executed.   However,  in
       earlier  implementations,  when  such  an  assignment  appeared before any file names, the
       assignment would happen before the BEGIN block was run.  Applications came  to  depend  on
       this  “feature.”   When  awk  was  changed  to  match its documentation, the -v option for
       assigning variables before program execution was added to  accommodate  applications  that
       depended  upon  the  old  behavior.   (This  feature  was  agreed  upon  by  both the Bell
       Laboratories and the GNU developers.)

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

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

       Other new 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 ANSI 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  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).

       · The \x escape sequence.  (Disabled with --posix.)

       · The fflush() function.  (Disabled with --posix.)

       · The ability to continue lines after ?  and :.  (Disabled with --posix.)

       · Octal and hexadecimal constants in AWK programs.

       · The ARGIND, BINMODE, ERRNO, LINT, RT and TEXTDOMAIN variables are not special.

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

       · The FIELDWIDTHS variable and fixed-width field splitting.

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

       · The PROCINFO array is 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 co-processes.

       · 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 use of delete array to delete the entire contents of an array.

       · The use of nextfile to abandon processing of the current input file.

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

       · Localizable strings.

       · Adding new built-in functions dynamically with the extension() function.

       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  co-process  was  not  opened  with  a

       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 and --file options.

       For  socket  communication,  two  special environment variables can be used to control the
       number of retries (GAWK_SOCK_RETRIES), and the interval between retries (GAWK_MSEC_SLEEP).
       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 4.0.


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

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

       The initial DOS port was done by Conrad Kwok and Scott Garfinkle.  Scott Deifik  maintains
       the  port  to  MS-DOS  using  DJGPP.  Eli Zaretskii maintains the port to MS-Windows using
       MinGW.  Pat Rankin did the port to VMS, and Michal Jaegermann did the port  to  the  Atari
       ST.   The port to OS/2 was done by Kai Uwe Rommel, with contributions and help from Darrel
       Hankerson.  Andreas Buening now maintains the OS/2 port.   The  late  Fred  Fish  supplied
       support  for  the Amiga, and Martin Brown provided the BeOS port.  Stephen Davies provided
       the original Tandem port,  and  Matthew  Woehlke  provided  changes  for  Tandem's  POSIX-
       compliant systems.  Dave Pitts provided the port to z/OS.

       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.  Instead, please use the electronic mail addresses given above.

       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.

       Syntactically  invalid  single  character  programs  tend  to  overflow  the  parse stack,
       generating a rather unhelpful  message.   Such  programs  are  surprisingly  difficult  to
       diagnose in the completely general case, and the effort to do so really is not worth it.


       egrep(1), getpid(2), getppid(2), getpgrp(2), getuid(2), geteuid(2), getgid(2), getegid(2),
       getgroups(2), usleep(3)

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

       GAWK:  Effective  AWK Programming, Edition 4.0, shipped with the gawk source.  The current
       version of this document is 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 of Bell Laboratories  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 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.