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AWK(1)									AWK(1)

awk

NAME
       awk - pattern-directed scanning and processing language

SYNOPSIS
       awk [ -F	fs ] [ -v var=value ] [	'prog' | -f progfile ] [ file ...  ]

DESCRIPTION
       Awk scans each input file for lines that	match any of a set of patterns
       specified literally in prog or in one or	more  files  specified	as  -f
       progfile.   With	 each  pattern	there can be an	associated action that
       will be performed when a	line of	a file matches the pattern.  Each line
       is  matched  against the	pattern	portion	of every pattern-action	state-
       ment; the associated action is performed	for each matched pattern.  The
       file  name  - means the standard	input.	Any file of the	form var=value
       is treated as an	assignment, not	a filename, and	 is  executed  at  the
       time  it	 would	have been opened if it were a filename.	 The option -v
       followed	by var=value is	an assignment to be done before	prog  is  exe-
       cuted;  any  number  of	-v  options  may be present.  The -F fs	option
       defines the input field separator to be the regular expression fs.

       An input	line is	normally made up of fields separated by	 white	space,
       or by regular expression	FS.  The fields	are denoted $1,	$2, ..., while
       $0 refers to the	entire line.  If FS is null, the input line  is	 split
       into one	field per character.

       A pattern-action	statement has the form

	      pattern {	action }

       A  missing  {  action  }	means print the	line; a	missing	pattern	always
       matches.	 Pattern-action	statements are separated by newlines or	 semi-
       colons.

       An  action  is a	sequence of statements.	 A statement can be one	of the
       following:

	      if( expression ) statement [ else	statement ]
	      while( expression	) statement
	      for( expression ;	expression ; expression	) statement
	      for( var in array	) statement
	      do statement while( expression )
	      break
	      continue
	      {	[ statement ...	] }
	      expression	      #	commonly var = expression
	      print [ expression-list ]	[ > expression ]
	      printf format [ ,	expression-list	] [ > expression ]
	      return [ expression ]
	      next		      #	skip remaining patterns	on this	input line
	      nextfile		      #	skip rest of this file,	open next, start at top
	      delete array[ expression ]# delete an array element
	      delete array	      #	delete all elements of array
	      exit [ expression	]     #	exit immediately; status is expression

       Statements are terminated by semicolons,	newlines or right braces.   An
       empty  expression-list stands for $0.  String constants are quoted " ",
       with the	usual C	escapes	recognized within.  Expressions	take on	string
       or numeric values as appropriate, and are built using the operators + -
       * / % ^ (exponentiation), and concatenation (indicated by white space).
       The  operators  !  ++  -- += -= *= /= %=	^= > >=	< <= ==	!= ?: are also
       available in expressions.  Variables may	 be  scalars,  array  elements
       (denoted	 x[i])	or  fields.   Variables	 are  initialized  to the null
       string.	Array subscripts may be	any string, not	 necessarily  numeric;
       this allows for a form of associative memory.  Multiple subscripts such
       as [i,j,k] are permitted; the constituents are concatenated,  separated
       by the value of SUBSEP.

       The  print statement prints its arguments on the	standard output	(or on
       a file if >file or >>file is present or on a pipe if |cmd is  present),
       separated  by the current output	field separator, and terminated	by the
       output record separator.	 file and cmd may be literal names  or	paren-
       thesized	 expressions;  identical string	values in different statements
       denote the same open file.  The printf statement	formats	its expression
       list  according	to  the	format (see printf(3)).	 The built-in function
       close(expr) closes the  file  or	 pipe  expr.   The  built-in  function
       fflush(expr) flushes any	buffered output	for the	file or	pipe expr.

       The  mathematical  functions  exp,  log,	 sqrt, sin, cos, and atan2 are
       built in.  Other	built-in functions:

       length the length of its	argument taken as a string, or	of  $0	if  no
	      argument.

       rand   random number on (0,1)

       srand  sets seed	for rand and returns the previous seed.

       int    truncates	to an integer value

       substr(s, m, n)
	      the n-character substring	of s that begins at position m counted
	      from 1.

       index(s,	t)
	      the position in s	where the string t occurs, or  0  if  it  does
	      not.

       match(s,	r)
	      the position in s	where the regular expression r occurs, or 0 if
	      it does not.  The	variables RSTART and RLENGTH are  set  to  the
	      position and length of the matched string.

       split(s,	a, fs)
	      splits  the  string s into array elements	a[1], a[2], ..., a[n],
	      and returns n.  The separation is	done with the regular  expres-
	      sion  fs	or with	the field separator FS if fs is	not given.  An
	      empty string as field separator splits the string	into one array
	      element per character.

       sub(r, t, s)
	      substitutes t for	the first occurrence of	the regular expression
	      r	in the string s.  If s is not given, $0	is used.

       gsub   same as sub except that all occurrences of the  regular  expres-
	      sion  are	 replaced;  sub	and gsub return	the number of replace-
	      ments.

       sprintf(fmt, expr, ... )
	      the string resulting from	formatting expr	...  according to  the
	      printf(3)	format fmt

       system(cmd)
	      executes cmd and returns its exit	status

       tolower(str)
	      returns  a copy of str with all upper-case characters translated
	      to their corresponding lower-case	equivalents.

       toupper(str)
	      returns a	copy of	str with all lower-case	characters  translated
	      to their corresponding upper-case	equivalents.

       The ``function''	getline	sets $0	to the next input record from the cur-
       rent input file;	getline	<file sets $0 to the next  record  from	 file.
       getline	x  sets	 variable x instead.  Finally, cmd | getline pipes the
       output of cmd into getline; each	call of	getline	returns	the next  line
       of  output  from	cmd.  In all cases, getline returns 1 for a successful
       input, 0	for end	of file, and -1	for an error.

       Patterns	are arbitrary Boolean combinations (with ! || &&)  of  regular
       expressions  and	relational expressions.	 Regular expressions are as in
       egrep; see grep(1).  Isolated regular expressions in a pattern apply to
       the  entire  line.   Regular  expressions  may also occur in relational
       expressions, using the operators	~ and !~.  /re/	is a constant  regular
       expression;  any	string (constant or variable) may be used as a regular
       expression, except in the position of an	isolated regular expression in
       a pattern.

       A  pattern  may	consist	 of two	patterns separated by a	comma; in this
       case, the action	is performed for all lines from	an occurrence  of  the
       first pattern though an occurrence of the second.

       A relational expression is one of the following:

	      expression matchop regular-expression
	      expression relop expression
	      expression in array-name
	      (expr,expr,...) in array-name

       where  a	 relop	is  any	 of  the  six relational operators in C, and a
       matchop is either ~ (matches) or	!~ (does not match).  A	conditional is
       an  arithmetic expression, a relational expression, or a	Boolean	combi-
       nation of these.

       The special patterns BEGIN and END  may	be  used  to  capture  control
       before  the first input line is read and	after the last.	 BEGIN and END
       do not combine with other patterns.

       Variable	names with special meanings:

       CONVFMT
	      conversion format	used when converting numbers (default %.6g)

       FS     regular expression used to separate  fields;  also  settable  by
	      option -Ffs.

       NF     number of	fields in the current record

       NR     ordinal number of	the current record

       FNR    ordinal number of	the current record in the current file

       FILENAME
	      the name of the current input file

       RS     input record separator (default newline)

       OFS    output field separator (default blank)

       ORS    output record separator (default newline)

       OFMT   output format for	numbers	(default %.6g)

       SUBSEP separates	multiple subscripts (default 034)

       ARGC   argument count, assignable

       ARGV   argument	array, assignable; non-null members are	taken as file-
	      names

       ENVIRON
	      array of environment variables; subscripts are names.

       Functions may be	defined	(at the	position of  a	pattern-action	state-
       ment) thus:

	      function foo(a, b, c) { ...; return x }

       Parameters  are	passed	by  value  if scalar and by reference if array
       name; functions may be called recursively.  Parameters are local	to the
       function;  all other variables are global.  Thus	local variables	may be
       created by providing excess parameters in the function definition.

EXAMPLES
       length($0) > 72
	      Print lines longer than 72 characters.

       { print $2, $1 }
	      Print first two fields in	opposite order.

       BEGIN { FS = ",[	\t]*|[ \t]+" }
	     { print $2, $1 }
	      Same, with input fields separated	by  comma  and/or  blanks  and
	      tabs.

	    { s	+= $1 }
       END  { print "sum is", s, " average is",	s/NR }
	      Add up first column, print sum and average.

       /start/,	/stop/
	      Print all	lines between start/stop pairs.

       BEGIN	 {    #	Simulate echo(1)
	    for	(i = 1;	i < ARGC; i++) printf "%s ", ARGV[i]
	    printf "\n"
	    exit }

SEE ALSO
       lex(1), sed(1)
       A.  V. Aho, B. W. Kernighan, P. J. Weinberger, The AWK Programming Lan-
       guage, Addison-Wesley, 1988.  ISBN 0-201-07981-X

BUGS
       There are no explicit conversions  between  numbers  and	 strings.   To
       force  an expression to be treated as a number add 0 to it; to force it
       to be treated as	a string concatenate ""	to it.
       The scope rules for variables in	functions are a	botch; the  syntax  is
       worse.

									AWK(1)

NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO | BUGS

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