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GAWK(1)                        Utility Commands                        GAWK(1)

       gawk - pattern scanning and processing language

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

       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 lan-
       guage.  It conforms to the definition of  the  language  in  the  POSIX
       1003.1  Standard.   This version in turn is based on the description in
       The AWK Programming Language, by Aho, Kernighan, and Weinberger.   Gawk
       provides  the  additional features found in the current version of 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

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

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

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

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

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

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

       -v var=val
       --assign var=val
              Assign  the  value  val to the variable var, before execution of
              the program begins.  Such variable values are available  to  the
              BEGIN 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  attempt-
              ing  to  process  strings  as multibyte characters.  The --posix
              option overrides this one.

              Run in compatibility mode.  In compatibility mode, gawk  behaves
              identically to 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 pro-
              cessed.  This should be used with #!  scripts, particularly  for
              CGI applications, to avoid passing in options or source code (!)
              on the command line from a URL.  This option  disables  command-
              line variable assignments.

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

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

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

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

              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

              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

              Send profiling data to prof_file.  The default  is  awkprof.out.
              When  run with gawk, the profile is just a "pretty printed" ver-
              sion 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

              o \x escape sequences are not recognized.

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

              o You cannot continue lines after ?  and :.

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

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

              o 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 --traditional.

       --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 Stan-
              dards, these options cause an immediate, successful exit.)

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

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

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

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

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

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

       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 com-
       piles 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  val-
       ues  to  the  variables  AWK  uses  to control how input is broken into
       fields and records.  It is also useful for controlling state if  multi-
       ple passes are needed over a single data file.

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

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

       For  each record in the input, gawk tests to see if it matches any pat-
       tern in the AWK program.  For each pattern that the record matches, 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 any).

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

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

       AWK variables are dynamic; they come into existence when they are first
       used.   Their  values  are either floating-point numbers or strings, or
       both, depending upon how they are used.  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 compatibil-
       ity mode, only the first character of its string value is used for sep-
       arating  records.   If  RS  is set to the null string, then records are
       separated by blank lines.  When RS is set to the null string, the  new-
       line  character  always acts as a field separator, in addition to what-
       ever value FS may have.

       As each input record is read, gawk splits the record into fields, using
       the value of the FS variable as the field separator.  If FS is a single
       character, fields are separated by that character.  If FS is  the  null
       string,  then each individual character becomes a separate field.  Oth-
       erwise, FS is expected to be a full regular expression.  In the special
       case  that FS is a single space, fields are separated by runs of spaces
       and/or tabs and/or newlines.  (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 num-
       bers, 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 FIELDWIDTHS.

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

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

              n = 5
              print $n

       prints the fifth field in the input record.

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

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

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

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

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

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

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

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

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

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

       FILENAME    The name of the current input file.  If no files are speci-
                   fied  on  the  command  line, the value of FILENAME is "-".
                   However, FILENAME  is  undefined  inside  the  BEGIN  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,

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

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

       NF          The number of fields in the current input record.

       NR          The total number of input records seen so far.

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

       OFS         The output field separator, a space by default.

       ORS         The output record separator, by default a newline.

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

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

                                       The  default  time  format  string  for

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

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

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

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

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

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

                   PROCINFO["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 cor-
                   responding 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

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

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

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

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

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

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

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

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

              if (val in array)
                   print array[val]

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

       The in construct may also be used in a for loop to iterate over all the
       elements of an array.

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

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

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

       NOTE:  When  operating  in POSIX mode (such as with the --posix 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 fol-
            lowing 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 expres-
       sions (e.g., /[ \t\f\n\r\v]/ matches whitespace characters).

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

       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 ignored.

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

       AWK patterns may be one of the following:

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

       BEGIN  and  END  are two special kinds of patterns which are not tested
       against the input.  The action parts of all BEGIN patterns  are  merged
       as  if  all  the  statements  had been written in a single BEGIN 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 BEGIN-
       FILE  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

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

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

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

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

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

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

       c          matches the non-metacharacter c.

       \c         matches the literal character c.

       .          matches any character including newline.

       ^          matches the beginning of a string.

       $          matches the end of a string.

       [abc...]   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 expres-
                  sion.  If there is one number in the braces,  the  preceding
                  regular  expression r is repeated n times.  If there are two
                  numbers separated by a comma, r is repeated n  to  m  times.
                  If  there  is  one  number  followed  by  a comma, then r is
                  repeated at least n times.

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

       \B         matches the empty string within a word.

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

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

       \s         matches any whitespace character.

       \S         matches any nonwhitespace character.

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

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

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

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

       The escape sequences that are valid in string constants (see 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 charac-
       ters that have a specific attribute, but where  the  actual  characters
       themselves  can  vary from country to country and/or from character set
       to character set.  For example, the notion of  what  is  an  alphabetic
       character differs in the USA and in France.

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

       [:alnum:]  Alphanumeric characters.

       [:alpha:]  Alphabetic characters.

       [:blank:]  Space or tab characters.

       [:cntrl:]  Control characters.

       [:digit:]  Numeric characters.

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

       [:lower:]  Lowercase alphabetic characters.

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

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

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

       [:upper:]  Uppercase alphabetic characters.

       [:xdigit:] Characters that are hexadecimal digits.

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

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

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

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

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

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

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

       No options
              In  the  default  case, gawk 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 provided.

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

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

       (...)       Grouping

       $           Field reference.

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

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

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

       * / %       Multiplication, division, and modulus.

       + -         Addition and subtraction.

       space       String concatenation.

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

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

       ~ !~        Regular  expression match, negated match.  NOTE: Do not use
                   a constant regular expression (/foo/) on the left-hand side
                   of  a  ~  or !~.  Only use one on the right-hand side.  The
                   expression /foo/ ~ exp has  the  same  meaning  as  (($0  ~
                   /foo/) ~ exp).  This is usually not what 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  expres-
                   sion  is  expr2,  otherwise it is expr3.  Only one of expr2
                   and expr3 is evaluated.

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

   Control Statements
       The control statements are as follows:

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

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

       close(file [, how])   Close file, pipe or 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 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,

       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

       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

       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, below.)

       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 prob-

       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 EOF.

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

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

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

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

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

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

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

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

       %s      A character string.

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

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

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

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

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

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

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

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

       0      A  leading 0 (zero) acts as a flag, 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 sig-
              nificant digits.  For the %d, %i, %o, %u, %x, and %X formats, it
              specifies  the  minimum  number  of digits to print.  For %s, it
              specifies the maximum number of characters from the string  that
              should be printed.

       The dynamic width and prec capabilities of the 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  pre-
       cision,  supply the count$ after the * in the format string.  For exam-
       ple, "%3$*2$.*1$s".

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

       /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 genera-

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

       asort(s [, d [, how] ]) Return the number of  elements  in  the  source
                               array  s.   Sort the contents of s using gawk's
                               normal rules for comparing values, and  replace
                               the indices of the sorted values s with sequen-
                               tial integers starting with 1. If the  optional
                               destination  array  d  is specified, 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 val-
                               ues are those of  the  original  indices.   The
                               original values are lost; thus provide a second
                               array if you wish  to  preserve  the  original.
                               The  purpose  of the optional string how is the
                               same as described 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 begin-
                               ning with g or G, then replace all matches of r
                               with  s.   Otherwise,  h is a number indicating
                               which match of r to replace.  If t is not  sup-
                               plied,  use $0 instead.  Within the replacement
                               text s, the sequence \n, where  n  is  a  digit
                               from  1  to 9, may be used to indicate just the
                               text that matched the n'th parenthesized subex-
                               pression.    The  sequence  \0  represents  the
                               entire matched text, as does the  character  &.
                               Unlike sub() and gsub(), the modified string is
                               returned as the result of the function, and the
                               original target string is not changed.

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

       index(s, t)             Return  the index of the string t in the string
                               s, or 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

       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  sub-

       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 identi-
                               cally to field splitting with  FPAT,  described

       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 string.

       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  func-
       tions 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  respec-
                 tively  the  full year including century, the month from 1 to
                 12, the day of the month from 1 to 31, the hour  of  the  day
                 from  0  to 23, the minute from 0 to 59, the second from 0 to
                 60, and an optional daylight  saving  flag.   The  values  of
                 these  numbers  need  not be within the ranges specified; for
                 example, an hour of -1 means 1  hour  before  midnight.   The
                 origin-zero  Gregorian  calendar is assumed, with year 0 pre-
                 ceding year 1 and year -1 preceding  year  0.   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  sys-
                 time().   If timestamp is missing, the current time of day is
                 used.  If format is missing, a default format  equivalent  to
                 the  output of date(1) is used.  The default format is avail-
                 able in PROCINFO["strftime"].  See the specification for  the
                 strftime() function in 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  inte-
       gers,  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

       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

       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'' loca-
              tions  (e.g.,  during  testing).  It returns the directory where
              domain is ``bound.''
              The default domain is the value of TEXTDOMAIN.  If directory  is
              the  null string (""), then bindtextdomain() returns the current
              binding for the given domain.

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

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

       Functions in AWK are defined as follows:

              function name(parameter list) { statements }

       Functions 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  pro-
       vision for local variables is rather clumsy: They are declared as extra
       parameters in the parameter list.  The convention is to separate  local
       variables  from  real parameters by extra spaces in the parameter list.
       For example:

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

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

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

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

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

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

              {    ...
                   the_func = "myfunc"
                   @the_func()    # call through the_func to myfunc

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

       The word func may be used in place of function.

       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  contin-
       ues  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 program.

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

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

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

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

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

       A  primary  goal  for gawk is compatibility with the POSIX standard, as
       well as with the latest version of UNIX awk.  To this end, gawk  incor-
       porates  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

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

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

       Other 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 sup-
       ports: It is possible to call the length() built-in function  not  only
       with no argument, but even without parentheses!  Thus,

              a = length     # Holy Algol 60, Batman!

       is the same as either of

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

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

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

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

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

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

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

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

       o The ability to  continue  lines  after  ?   and  :.   (Disabled  with

       o Octal and hexadecimal constants in AWK programs.

       o The ARGIND, BINMODE, ERRNO, LINT, RT and TEXTDOMAIN variables are not

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

       o The FIELDWIDTHS variable and fixed-width field splitting.

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

       o The PROCINFO array is not available.

       o The use of RS as a regular expression.

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

       o The |& operator for creating co-processes.

       o The BEGINFILE and ENDFILE special patterns are not available.

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

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

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

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

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

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

       o The use of delete array to delete the entire contents of an array.

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

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

       o Localizable strings.

       o Adding  new built-in functions dynamically with the extension() func-

       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 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
       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  com-
       patible  with  the new version of UNIX awk.  Arnold Robbins is the cur-
       rent maintainer.

       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  pro-
       vided the BeOS port.  Stephen Davies provided the original Tandem port,
       and Matthew Woehlke provided changes for Tandem's POSIX-compliant  sys-
       tems.  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  bug-
       gawk@gnu.org.   Please  include your operating system and its revision,
       the version of gawk (from gawk --version), which C compiler you used to
       compile  it,  and a test program and data that are as small as possible
       for reproducing the problem.

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

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

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

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

       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 dur-
       ing testing and debugging.  We thank him.

       Copyright (C) 1989, 1991, 1992, 1993, 1994,  1995,  1996,  1997,  1998,
       1999,  2001,  2002, 2003, 2004, 2005, 2007, 2009, 2010, 2011 Free Soft-
       ware Foundation, Inc.

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

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

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

Free Software Foundation          Nov 10 2011                          GAWK(1)

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