gawk


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 1003.2 Command Language And Utilities
  Standard.  This version in turn is based on the description
  in The AWK Programming Language, by Aho, Kernighan, and
  Weinberger, with the additional features defined in the
  System V Release 4 version of UNIX awk.  Gawk also provides
  some 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.

OPTIONS
  Gawk options may be either the traditional POSIX one letter
  options, or the GNU style long options.  POSIX style options
  start with a single ``-'', while GNU long options start with
  ``--''.  GNU style long options are provided for both GNU-
  specific features and for POSIX mandated features.  Other
  implementations of the AWK language are likely to only
  accept the traditional one letter options.

  Following the POSIX standard, gawk-specific options are
  supplied via arguments to the -W option.  Multiple -W
  options may be supplied, or multiple arguments may be
  supplied together if they are separated by commas, or
  enclosed in quotes and separated by white space.  Case is
  ignored in arguments to the -W option.  Each -W option has a
  corresponding GNU style long option, as detailed below.
  Arguments to GNU style 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.

  Gawk accepts the following options.

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

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

  -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.

  -mf=NNN
  -mr=NNN
	   Set various memory limits to the value NNN.  The f flag
	   sets the maximum number of fields, and the r flag sets
	   the maximum record size.  These two flags and the -m
	   option are from the AT&T Bell Labs research version of
	   UNIX awk.  They are ignored by gawk, since gawk has no
	   pre-defined limits.
  -W compat
  --compat    Run in compatibility mode.  In compatibility
			  mode, gawk behaves identically to UNIX awk; none
			  of the GNU-specific extensions are recognized.
			  See GNU EXTENSIONS, below, for more information.

  -W copyleft
  -W copyright
  --copyleft
  --copyright Print the short version of the GNU copyright
			  information message on the error output.

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

  -W lint
  --lint      Provide warnings about constructs that are
			  dubious or non-portable to other AWK
			  implementations.
  -W posix
  --posix     This turns on compatibility mode, with the
			  following additional restrictions:

			  + \x escape sequences are not recognized.

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

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

  -W source=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 size AWK programs used in shell scripts.

9 The -W source= form of this option uses the rest

			  of the command line argument for program-text;
			  no other options to -W will be recognized in the
			  same argument.

  -W version
  --version   Print version information for this particular
			  copy of gawk on the error 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.  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 is mainly
			  for consistency with the argument parsing
			  convention used by most other POSIX programs.

  In compatibility mode, any other options are flagged as
  illegal, 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.

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

	   pattern   { action statements }
	   function name(parameter list)) { statements }

  Gawk first reads the program source from the program-file(s)
  if specified, from arguments to -W source=, or from the
  first non-option argument on the command line.  The -f and
  -W source= options may be used multiple times on the command
  line.  Gawk will read the program text as if all the
  program-files and command line source texts had been
  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.

  The environment variable AWKPATH specifies a search path to
  use when finding source files named with the -f option.  If
  this variable does not exist, the default path is
  ".:/usr/lib/awk:/usr/local/lib/awk".  If a file name given
  to the -f option contains a ``/'' character, no path search
  is performed.

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

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

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

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

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

VARIABLES 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.  Several pre-defined
  variables are set as a program runs; these will be described
  as needed and summarized below.

Fields
  As each input line is read, gawk splits the line into

  separator.  If FS is a single character, fields are
  separated by that character.  Otherwise, FS is expected to
  be a full regular expression.  In the special case that FS
  is a single blank, fields are separated by runs of blanks
  and/or tabs.  Note that the value of IGNORECASE (see below)
  will also affect how fields are split when FS 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 will split up the record using the specified widths.
  The value of FS is ignored.  Assigning a new value to FS
  overrides the use of FIELDWIDTHS, and restores the default
  behavior.

  Each field in the input line may be referenced by its
  position, $1, $2, and so on.  $0 is the whole line. The
  value of a field may be assigned to as well.  Fields need
  not be referenced by constants:

	   n = 5
	   print $n

  prints the fifth field in the input line.  The variable NF
  is set to the total number of fields in the input line.

  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) will increase the value
  of NF, create any intervening fields with the null string as
  their value, and cause 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.

Built-in Variables
  AWK'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.

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


			  environment.  The array is indexed by the
			  environment variables, each element being the
			  value of that variable (e.g., ENVIRON["HOME"]
			  might be /u/arnold).  Changing this array does
			  not affect the environment seen by programs
			  which gawk spawns via redirection or the
			  system() function.  (This may change in a future
			  version of gawk.)

  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.

  FIELDWIDTHS A white-space separated list of fieldwidths.
			  When set, gawk parses the input into fields of
			  fixed width, instead of using the value of the
			  FS variable as the field separator.  The fixed
			  field width facility is still experimental;
			  expect the semantics to change as gawk evolves
			  over time.

  FILENAME    The name of the current input file.  If no files
			  are specified on the command line, the value of
			  FILENAME is ``-''.  However, FILENAME is
			  undefined inside the BEGIN block.

  FNR         The input record number in the current input
			  file.

  FS          The input field separator, a blank by default.

  IGNORECASE  Controls the case-sensitivity of all regular
			  expression operations. If IGNORECASE has a non-
			  zero value, then pattern matching in rules,
			  field splitting with FS, regular expression
			  matching with ~ and !~, and the gsub(), index(),
			  match(), split(), and sub() pre-defined
			  functions will all ignore case when doing
			  regular expression operations.  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
			  operations are normally case-sensitive.

  NF          The number of fields in the current input
			  record.

  NR          The total number of input records seen so far.


			  default.

  OFS         The output field separator, a blank by default.

  ORS         The output record separator, by default a
			  newline.

  RS          The input record separator, by default a
			  newline.  RS is exceptional in that only the
			  first character of its string value is used for
			  separating records.  (This will probably change
			  in a future release of gawk.) If RS is set to
			  the null string, then records are separated by
			  blank lines.  When RS is set to the null string,
			  then the newline character always acts as a
			  field separator, in addition to whatever value
			  FS may have.

  RSTART      The index of the first character matched by
			  match(); 0 if no match.

  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".

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 in an if or while
  statement to see if an array has an index consisting of a
  particular value.

	   if (val in array)
			print array[val]



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

  An element may be deleted from an array using the delete
  statement.  The delete statement may also be used to delete
  the entire contents of an array.

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

  To force a variable to be treated as a number, add 0 to it;
  to force it to be treated as a string, concatenate it with
  the null string.

  When a string must be converted to a number, the conversion
  is accomplished using atof(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".

  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.  According to the POSIX standard,
  even if two strings are numeric strings, a numeric
  comparison is performed.  However, this is clearly
  incorrect, and gawk does not do this.

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

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, the action will be executed for every single line
  of input.  A missing action is equivalent to

	   { print }

  which prints the entire line.

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

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

  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
  line 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 except newline.

  ^          matches the beginning of a line or a string.

  $          matches the end of a line or a string.

  [abc...]   character class, matches any of the characters
			 abc....

  [^abc...]  negated character class, matches any character
			 except abc... and newline.

  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.

  below) are also legal in regular expressions.

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 increasing precedence, are

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

  ?:          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.

  ||          Logical OR.

  &&          Logical AND.

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

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

  blank       String concatenation.

  + -         Addition and subtraction.

  * / %       Multiplication, division, and modulus.

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

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

  ++ --       Increment and decrement, both prefix and


  $           Field reference.

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 }

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

  close(filename))       Close file (or pipe, see below).

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

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

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

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

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

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


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

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

  printf fmt, expr-list Format and print.

  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.)

  Other input/output redirections are also allowed. For print
  and printf, >>file appends output to the file, while |
  command writes on a pipe.  In a similar fashion, command |
  getline pipes into getline.  The getline command will return
  0 on end of file, and -1 on an error.

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

  %c   An ASCII 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   A decimal number (the integer part).

  %i   Just like %d.

  %e   A floating point number of the form [-]d.ddddddE[+-]dd.

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

  %g   Use e or f conversion, whichever is shorter, with
	   nonsignificant zeros suppressed.

  %o   An unsigned octal number (again, an integer).



  %x   An unsigned hexadecimal number (an integer).

  %X   Like %x, but using ABCDEF instead of abcdef.

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

  There are optional, additional parameters that may lie
  between the % and the control letter:

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

  width
	   The field should be padded to this width. If the number
	   has a leading zero, then the field will be padded with
	   zeros.  Otherwise it is padded with blanks.  This
	   applies even to the non-numeric output formats.

  .prec
	   A number indicating the maximum width of strings or
	   digits to the right of the decimal point.

  The dynamic width and prec capabilities of the ANSI C
  printf() routines are supported.  A * in place of either the
  width or prec specifications will cause their values to be
  taken from the argument list to printf or sprintf().

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).  Other special filenames
  provide access information about the running gawk process.
  The filenames are:

  /dev/pid    Reading this file returns the process ID of the
			  current process, in decimal, terminated with a
			  newline.

  /dev/ppid   Reading this file returns the parent process ID
			  of the current process, in decimal, terminated
			  with a newline.

  /dev/pgrpid Reading this file returns the process group ID
			  of the current process, in decimal, terminated
			  with a newline.

  /dev/user   Reading this file returns a single record
			  terminated with a newline.  The fields are

			  getuid(2) system call, $2 is the value of the
			  geteuid(2) system call, $3 is the value of the
			  getgid(2) system call, and $4 is the value of
			  the getegid(2) system call.  If there are any
			  additional fields, they are the group IDs
			  returned by getgroups(2).  Multiple groups may
			  not be supported on all systems.

  /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"

  These file names may also be used on the command line to
  name data files.

Numeric Functions
  AWK has the following pre-defined arithmetic functions:

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

  cos(expr))   returns the cosine in radians.

  exp(expr))   the exponential function.

  int(expr))   truncates to integer.

  log(expr))   the natural logarithm function.

  rand()      returns a random number between 0 and 1.

  sin(expr))   returns the sine in radians.

  sqrt(expr))  the square root function.

  srand(expr)) use expr as a new seed for the random number
			  generator. If no expr is provided, the time of
			  day will be used.  The return value is the


String Functions
  AWK has the following pre-defined string functions:

  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.

  index(s, t)             returns the index of the string t in
						  the string s, or 0 if t is not
						  present.

  length(s)               returns the length of the string s,
						  or the length of $0 if s is not
						  supplied.

  match(s, r)             returns the position in s where the
						  regular expression r occurs, or 0 if
						  r is not present, and sets the
						  values of RSTART and RLENGTH.

  split(s, a, r)          splits the string s into the array a
						  on the regular expression r, and
						  returns the number of fields. If r
						  is omitted, FS is used instead.  The
						  array a is cleared first.

  sprintf(fmt, expr-list)) prints expr-list according to fmt,
						  and returns the resulting string.

  sub(r, s, t)            just like gsub(), but only the first
						  matching substring is replaced.

  substr(s, i, n)         returns the n-character substring of
						  s starting at i.  If n is omitted,
						  the rest of s is used.

  tolower(str))            returns a copy of the string str,
						  with all the upper-case characters
						  in str translated to their
						  corresponding lower-case
						  counterparts.  Non-alphabetic
						  characters are left unchanged.

  toupper(str))            returns a copy of the string str,
						  with all the lower-case characters
						  in str translated to their
						  corresponding upper-case
						  counterparts.  Non-alphabetic


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

  systime() returns the current time of day as the number of
			seconds since the Epoch (Midnight UTC, January 1,
			1970 on POSIX systems).

  strftime(format, timestamp))
			formats timestamp according to the specification
			in format.  The timestamp should be of the same
			form as returned by systime().  If timestamp is
			missing, the current time of day is used.  See the
			specification for the strftime() function in ANSI
			C for the format conversions that are guaranteed
			to be available.  A public-domain version of
			strftime(3) and a man page for it are shipped with
			gawk; if that version was used to build gawk, then
			all of the conversions described in that man page
			are available to gawk.

String Constants
  String constants in AWK are sequences of characters enclosed
  between double quotes ("). 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   new line.

  \r   carriage return.

  \t   horizontal tab.

  \v   vertical tab.

  \xhex digits
	   The character represented by the string of hexadecimal
	   digits following the \x.  As in ANSI C, all following
	   hexadecimal digits are considered part of the escape
	   sequence.  (This feature should tell us something about

	   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).

FUNCTIONS
  Functions in AWK are defined as follows:

	   function name(parameter list)) { statements }

  Functions are executed when called from within the action
  parts of regular pattern-action statements. 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 & 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 white space.  This is to avoid 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.

  The word func may be used in place of function.

EXAMPLES
  Print and sort the login names of all users:

			{ 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 }

SEE ALSO
  egrep(1), getpid(2), getppid(2), getpgrp(2), getuid(2),
  geteuid(2), getgid(2), getegid(2), getgroups(2)

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

  The GAWK Manual, Edition 0.15, published by the Free
  Software Foundation, 1993.

POSIX COMPATIBILITY
  A primary goal for gawk is compatibility with the POSIX
  standard, as well as with the latest version of UNIX awk.
  To this end, gawk incorporates the following user visible
  features which are not described in the AWK book, but are
  part of awk in System V Release 4, and are in the POSIX
  standard.

  The -v option for assigning variables before program
  execution starts is new.  The book indicates that command
  line variable assignment happens when awk would otherwise
  open the argument as a file, which is after the BEGIN block
  is executed.  However, in earlier implementations, when such
  an assignment appeared before any file names, the assignment
  would happen before the BEGIN block was run.  Applications
  came to depend on this ``feature.'' When awk was changed to
  match its documentation, this option was added to
  accommodate applications that depended upon the old
  behavior.  (This feature was agreed upon by both the AT&T
  and GNU developers.)

  The -W option for implementation specific features is from
  the POSIX standard.

  When processing arguments, gawk uses the special option

  mode, it will warn about, but otherwise ignore, 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 System V Release 4 version of UNIX awk (and 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 AT&T's); the
  tolower() and toupper() built-in functions (from AT&T); and
  the ANSI C conversion specifications in printf (done first
  in AT&T's version).

GNU EXTENSIONS
  Gawk has some extensions to POSIX awk.  They are described
  in this section.  All the extensions described here can be
  disabled by invoking gawk with the -W compat option.

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

	   + The \x escape sequence.

	   + The systime() and strftime() functions.

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

	   + The ARGIND and ERRNO variables are not special.

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

	   + The FIELDWIDTHS variable and fixed width field
		 splitting.

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

	   + The use of next file to abandon processing of the
		 current input file.

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

  The AWK book does not define the return value of the close()

  or pclose(3), when closing a file or pipe, respectively.

  When gawk is invoked with the -W compat option, if the fs
  argument to the -F option is ``t'', then FS will be set to
  the tab character.  Since this is a rather ugly special
  case, it is not the default behavior.  This behavior also
  does not occur if -W posix has been specified.

HISTORICAL FEATURES
  There are two features of historical AWK implementations
  that gawk supports.  First, it is possible to call the
  length() built-in function not only with no argument, but
  even without parentheses!  Thus,

	   a = length

  is the same as either of

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

  This feature is marked as ``deprecated'' in the POSIX
  standard, and gawk will issue a warning about its use if -W
  lint is specified on the command line.

  The other feature is the use of either the continue or the
  break statements outside the body of a while, for, or do
  loop.  Traditional AWK implementations have treated such
  usage as equivalent to the next statement.  Gawk will
  support this usage if -W compat has been specified.

ENVIRONMENT VARIABLES
  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 will issue
  a warning message to this effect.

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

  If your system actually has support for /dev/fd and the
  associated /dev/stdin, /dev/stdout, and /dev/stderr files,
  you may get different output from gawk than you would get on
  a system without those files.  When gawk interprets these
  files internally, it synchronizes output to the standard
  output with output to /dev/stdout, while on a system with
  those files, the output is actually to different open files.
  Caveat Emptor.


  This man page documents gawk, version 2.15.

  Starting with the 2.15 version of gawk, the -c, -V, -C, -a,
  and -e options of the 2.11 version are no longer recognized.
  This fact will not even be documented in the manual page for
  the next major version.

AUTHORS
  The original version of UNIX awk was designed and
  implemented by Alfred Aho, Peter Weinberger, and Brian
  Kernighan of AT&T Bell Labs. 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.

  The initial DOS port was done by Conrad Kwok and Scott
  Garfinkle.  Scott Deifik is the current DOS maintainer.  Pat
  Rankin did the port to VMS, and Michal Jaegermann did the
  port to the Atari ST.  The port to OS/2 was done by Kai Uwe
  Rommel, with contributions and help from Darrel Hankerson.

BUG REPORTS
  If you find a bug in gawk, please send electronic mail to
  bug-gnu-utils@prep.ai.mit.edu, with a carbon copy to
  arnold@gnu.ai.mit.edu.  Please include your operating system
  and its revision, the version of gawk, what 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 two things. First,
  verify that you have the latest version of gawk.  Many bugs
  (usually subtle ones) are fixed at each release, and if
  your's is out of date, the problem may already have been
  solved.  Second, 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.

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