Provided by: gawk_4.1.4+dfsg-1build1_amd64 bug

NAME

       gawk - pattern scanning and processing language

SYNOPSIS

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

DESCRIPTION

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

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

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

OPTION FORMAT

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

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

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

OPTIONS

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

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

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

       -v var=val
       --assign var=val
              Assign the value val to the variable var, before execution of the  program  begins.
              Such variable values are available to the BEGIN rule of an AWK program.

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

       -c
       --traditional
              Run  in  compatibility  mode.   In  compatibility mode, gawk behaves identically to
              Brian Kernighan's awk; none of the GNU-specific extensions are recognized.  See GNU
              EXTENSIONS, below, for more information.

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

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

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

       -e program-text
       --source program-text
              Use program-text  as  AWK  program  source  code.   This  option  allows  the  easy
              intermixing  of  library functions (used via the -f and --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.

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

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

       -i include-file
       --include include-file
              Load an awk source library.  This  searches  for  the  library  using  the  AWKPATH
              environment  variable.   If  the initial search fails, another attempt will be made
              after appending the .awk  suffix.   The  file  will  be  loaded  only  once  (i.e.,
              duplicates  are  eliminated),  and  the  code  does not constitute the main program
              source.

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

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

       -M
       --bignum
              Force  arbitrary precision arithmetic on numbers. This option has no effect if gawk
              is not compiled to use the GNU MPFR and MP libraries.

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

       -N
       --use-lc-numeric
              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.

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

       -O
       --optimize
              Enable  optimizations  upon the internal representation of the program.  Currently,
              this includes simple constant-folding, and  tail  call  elimination  for  recursive
              functions. The gawk maintainer hopes to add additional optimizations over time.

       -p[prof-file]
       --profile[=prof-file]
              Start  a  profiling session, and send the profiling data to prof-file.  The default
              is awkprof.out.  The profile contains execution counts of  each  statement  in  the
              program in the left margin and function call counts for each user-defined function.

       -P
       --posix
              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 ^=.

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

       -S
       --sandbox
              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).

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

       -V
       --version
              Print  version information for this particular copy of gawk on the standard output.
              This is useful mainly for knowing if the current copy of gawk on your system is  up
              to  date  with  respect  to  whatever the Free Software Foundation is distributing.
              This is also useful when reporting bugs.  (Per  the  GNU  Coding  Standards,  these
              options cause an immediate, successful exit.)

       --     Signal  the  end  of  options. This is useful to allow further arguments to the AWK
              program itself to start with a “-”.  This provides consistency  with  the  argument
              parsing convention used by most other POSIX programs.

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

       For POSIX compatibility, the -W option may be used, followed by the name of a long option.

AWK PROGRAM EXECUTION

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

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

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

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

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

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

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

       Gawk executes AWK programs in  the  following  order.   First,  all  variable  assignments
       specified  via  the  -v  option  are  performed.   Next, gawk compiles the program into an
       internal form.  Then, gawk executes the code in the  BEGIN  rule(s)  (if  any),  and  then
       proceeds  to  read  each file named in the ARGV array (up to ARGV[ARGC]).  If there are no
       files named on the command line, gawk reads the standard input.

       If a filename on the command line has the  form  var=val  it  is  treated  as  a  variable
       assignment.   The  variable  var  will be assigned the value val.  (This happens after any
       BEGIN rule(s) have been run.)   Command  line  variable  assignment  is  most  useful  for
       dynamically assigning values to the variables AWK uses to control how input is broken into
       fields and records.  It is also useful for controlling state if multiple passes are needed
       over a single data file.

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

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

       For  each  record  in  the  input,  gawk tests to see if it matches any pattern in the AWK
       program.  For each pattern that the record matches, gawk executes the  associated  action.
       The patterns are tested in the order they occur in the program.

       Finally,  after  all the input is exhausted, gawk executes the code in the END rule(s) (if
       any).

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

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

VARIABLES, RECORDS AND FIELDS

       AWK variables are dynamic; they come into existence  when  they  are  first  used.   Their
       values  are either floating-point numbers or strings, or both, depending upon how they are
       used.  AWK also has one  dimensional  arrays;  arrays  with  multiple  dimensions  may  be
       simulated.   Gawk  provides true arrays of arrays; see Arrays, below.  Several pre-defined
       variables are set as a program runs; these are described as needed and summarized below.

   Records
       Normally, records are separated by newline characters.  You can control  how  records  are
       separated by assigning values to the built-in variable RS.  If RS is any single character,
       that character separates records.  Otherwise, RS is a regular  expression.   Text  in  the
       input   that   matches   this  regular  expression  separates  the  record.   However,  in
       compatibility mode, only the first character of its string value is  used  for  separating
       records.   If  RS  is  set  to the null string, then 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.

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

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

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

              n = 5
              print $n

       prints the fifth field in the input record.

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

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

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

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

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

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

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

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

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

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

       FNR         The input record number in the current input file.

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

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

       FUNCTAB     An array whose indices and corresponding values are the names of all the user-
                   defined  or  extension  functions  in  the program.  NOTE: You may not use the
                   delete statement with the FUNCTAB array.

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

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

       NF          The number of fields in the current input record.

       NR          The total number of input records seen so far.

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

       OFS         The output field separator, a space by default.

       ORS         The output record separator, by default a newline.

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

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

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

                   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["identifiers"]
                                        A  subarray, indexed by the names of all identifiers used
                                        in the text of the AWK program.  The values indicate what
                                        gawk  knows  about  the identifiers after it has finished
                                        parsing the program;  they  are  not  updated  while  the
                                        program  runs.   For  each  identifier,  the value of the
                                        element is one of the following:

                                        "array"
                                               The identifier is an array.

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

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

                                        "scalar"
                                               The identifier is a scalar.

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

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

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

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

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

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

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

                   PROCINFO["version"]  the version of gawk.

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

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

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

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

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

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

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

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

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

                   PROCINFO["command", "pty"]
                          Use a pseudo-tty for two-way  communication  with  command  instead  of
                          setting up two one-way pipes.

                   PROCINFO["input", "READ_TIMEOUT"]
                          The timeout in milliseconds for reading data from input, where input is
                          a redirection string or a filename. A value of zero or less  than  zero
                          means no timeout.

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

                               function cmp_func(i1, v1, i2, v2)

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

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

       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".

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

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

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

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

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

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

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

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

              if (val in array)
                   print array[val]

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

       The in construct may also be used in a for loop to iterate over all  the  elements  of  an
       array.  However, the (i, j) in array construct only works in tests, not in for loops.

       An  element may be deleted from an array using the delete statement.  The delete statement
       may also be used to delete the entire contents of an array, just by specifying  the  array
       name without a subscript.

       gawk  supports  true  multidimensional  arrays.  It  does  not require that such arrays be
       ``rectangular'' as in C or C++.  For example:

              a[1] = 5
              a[2][1] = 6
              a[2][2] = 7

       NOTE: You may need to tell gawk that an array element is really a subarray in order to use
       it  where  gawk  expects an array (such as in the second argument to split()).  You can do
       this by creating an element  in  the  subarray  and  then  deleting  it  with  the  delete
       statement.

   Variable Typing And Conversion
       Variables  and fields may be (floating point) numbers, or strings, or both.  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.

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

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

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

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

       NOTE:  When  operating in POSIX mode (such as with the --posix option), beware that locale
       settings may interfere with the way decimal numbers are treated: the decimal separator  of
       the numbers you are feeding to gawk must conform to what your locale would expect, be it a
       comma (,) or a period (.).

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

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

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

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

       \\   A literal backslash.

       \a   The “alert” character; usually the ASCII BEL character.

       \b   Backspace.

       \f   Form-feed.

       \n   Newline.

       \r   Carriage return.

       \t   Horizontal tab.

       \v   Vertical tab.

       \xhex digits
            The  character  represented by the string of hexadecimal digits following the \x.  As
            in ISO 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/.

PATTERNS AND ACTIONS

       AWK is a line-oriented language.  The pattern comes first, and then  the  action.   Action
       statements  are enclosed in { and }.  Either the pattern may be missing, or the action may
       be missing, but, of course, not both.  If the pattern is missing, the action  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 statements themselves.

   Patterns
       AWK patterns may be one of the following:

              BEGIN
              END
              BEGINFILE
              ENDFILE
              /regular expression/
              relational expression
              pattern && pattern
              pattern || pattern
              pattern ? pattern : pattern
              (pattern)
              ! pattern
              pattern1, pattern2

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

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

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

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

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

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

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

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

       c          Matches the non-metacharacter c.

       \c         Matches the literal character c.

       .          Matches any character including newline.

       ^          Matches the beginning of a string.

       $          Matches the end of a string.

       [abc...]   A character list: matches any of the characters  abc....   You  may  include  a
                  range of characters by separating them with a dash.

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

       r1|r2      Alternation: matches either r1 or r2.

       r1r2       Concatenation: matches r1, and then r2.

       r+         Matches one or more r's.

       r*         Matches zero or more r's.

       r?         Matches zero or one r's.

       (r)        Grouping: matches r.

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

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

       \B         Matches the empty string within a word.

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

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

       \s         Matches any whitespace character.

       \S         Matches any nonwhitespace character.

       \w         Matches any word-constituent character (letter, digit, or underscore).

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

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

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

       The  escape  sequences  that are valid in string constants (see String Constants) are also
       valid in regular expressions.

       Character classes are a feature introduced in the POSIX standard.  A character class is  a
       special  notation  for  describing lists of characters that have a specific attribute, but
       where the actual characters themselves can  vary  from  country  to  country  and/or  from
       character  set  to  character  set.   For  example,  the  notion  of what is an alphabetic
       character differs in the USA and in France.

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

       [:alnum:]  Alphanumeric characters.

       [:alpha:]  Alphabetic characters.

       [:blank:]  Space or tab characters.

       [:cntrl:]  Control characters.

       [:digit:]  Numeric characters.

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

       [:lower:]  Lowercase alphabetic characters.

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

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

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

       [:upper:]  Uppercase alphabetic characters.

       [:xdigit:] Characters that are hexadecimal digits.

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

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

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

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

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

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

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

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

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

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

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

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

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

       (...)       Grouping

       $           Field reference.

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

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

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

       * / %       Multiplication, division, and modulus.

       + -         Addition and subtraction.

       space       String concatenation.

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

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

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

       in          Array membership.

       &&          Logical AND.

       ||          Logical OR.

       ?:          The C conditional expression.  This has the form expr1 ? expr2  :  expr3.   If
                   expr1  is  true,  the value of the expression is expr2, otherwise it is expr3.
                   Only one of expr2 and expr3 is evaluated.

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

   Control Statements
       The control statements are as follows:

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

   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, RT.

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

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

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

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

       command |& getline [var]
                             Run command as a co-process piping the output either into $0 or var,
                             as  above, and RT.  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.  Upon reaching the end of the input data, gawk executes any
                             END rule(s).

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

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

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

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

       printf fmt, expr-list Format and print.  See The printf Statement, below.

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

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

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

       Additional output redirections are allowed for print and printf.

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

       print ... | command
              Writes on a pipe.

       print ... |& command
              Sends data to a 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 is set to a string describing the problem.

       NOTE:  Failure  in opening a two-way socket results in a non-fatal error being returned to
       the calling function. If using a pipe, 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 system library supports
               it, %F is available as well. This is like %f, but uses capital letters for special
               “not a number” and “infinity” values. If %F is not available, gawk uses %f.

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

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

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

       %s      A character string.

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

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

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

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

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

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

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

       #      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.

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

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

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

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

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

       -           The standard input.

       /dev/stdin  The standard input.

       /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:

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

       /inet/udp/lport/rhost/rport
       /inet4/udp/lport/rhost/rport
       /inet6/udp/lport/rhost/rport
              Similar, but use UDP/IP instead of TCP/IP.

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

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

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

       exp(expr)     The exponential function.

       int(expr)     Truncate to integer.

       log(expr)     The natural logarithm function.

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

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

       sqrt(expr)    Return the square root of expr.

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

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

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

       asorti(s [, d [, how] ])
                               Return the number of elements in the source array s.  The behavior
                               is the same as that of asort(), except that the array indices  are
                               used  for  sorting, not the array values.  When done, the array is
                               indexed numerically, and the values  are  those  of  the  original
                               indices.   The  original  values  are  lost; thus provide a second
                               array if you wish to preserve the original.  The  purpose  of  the
                               optional string how is the same as described 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.)   It
                               is a fatal error to use a regexp constant for t.

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

       match(s, r [, a])       Return the position in s where the regular expression r occurs, or
                               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) Print expr-list according to fmt, and return the resulting string.

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

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

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

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

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

       Gawk is multibyte aware.  This means that index(), length(), substr() and match() all work
       in terms of characters, not bytes.

   Time Functions
       Since  one  of  the primary uses of AWK programs is processing log files that contain time
       stamp information, gawk provides the following functions for  obtaining  time  stamps  and
       formatting them.

       mktime(datespec)
                 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 ISO C for the format conversions that are guaranteed
                 to be available.

       systime() Return the current time of  day  as  the  number  of  seconds  since  the  Epoch
                 (1970-01-01 00:00:00 UTC on POSIX systems).

   Bit Manipulations Functions
       Gawk  supplies  the following bit manipulation functions.  They work by converting double-
       precision floating point values to uintmax_t  integers,  doing  the  operation,  and  then
       converting the result back to floating point.  The functions are:

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

       compl(val)          Return the bitwise complement of val.

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

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

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

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

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

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

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

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

USER-DEFINED FUNCTIONS

       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
       above.

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

       Use return expr to return a value from a function.  The return value is  undefined  if  no
       value is provided, or if the function returns by “falling off” the end.

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

              {    ...
                   the_func = "myfunc"
                   @the_func()    # call through the_func to myfunc
                   ...
              }
       As  of  version  4.1.2,  this  works  with user-defined functions, built-in functions, and
       extension functions.

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

       The word func may be used in place of function, although this is deprecated.

DYNAMICALLY LOADING NEW FUNCTIONS

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

SIGNALS

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

INTERNATIONALIZATION

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

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

       always prints hello, world.  But,

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

       might print bonjour, monde in France.

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

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

                BEGIN { TEXTDOMAIN = "myprog" }

           This allows gawk to find the .gmo file associated with  your  program.   Without  this
           step,  gawk  uses the messages text domain, which likely does not contain translations
           for your program.

       2.  Mark all strings that should be translated with leading underscores.

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

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

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

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

POSIX COMPATIBILITY

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

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

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

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

       Other  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 ISO C conversion specifications in printf  (done  first  in
       the Bell Laboratories version).

HISTORICAL FEATURES

       There  is one feature of historical AWK implementations that gawk supports: It is possible
       to call the length() built-in function  not  only  with  no  argument,  but  even  without
       parentheses!  Thus,

              a = length     # Holy Algol 60, Batman!

       is the same as either of

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

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

GNU EXTENSIONS

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

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

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

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

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

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

       · Localizable strings.

       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' ....

ENVIRONMENT VARIABLES

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

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

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

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

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

EXIT STATUS

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

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

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

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

VERSION INFORMATION

       This man page documents gawk, version 4.1.

AUTHORS

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

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

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

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

BUG REPORTS

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

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

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

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

BUGS

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

SEE ALSO

       egrep(1),  sed(1),  getpid(2),  getppid(2),  getpgrp(2), getuid(2), geteuid(2), getgid(2),
       getegid(2), getgroups(2), 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 4.1, shipped with the gawk source.  The current
       version of this document is available online at http://www.gnu.org/software/gawk/manual.

EXAMPLES

       Print and sort the login names of all users:

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

       Count lines in a file:

                 { nlines++ }
            END  { print nlines }

       Precede each line by its number in the file:

            { print FNR, $0 }

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

            { print NR, $0 }

       Run an external command for particular lines of data:

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

ACKNOWLEDGEMENTS

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

COPYING PERMISSIONS

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