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awk(1)									awk(1)

Name
       awk - pattern scanning and processing language

Syntax
       awk [-Fc] [-f prog] [-] [file...]

Description
       The  command scans each input file for lines that match any of a set of
       patterns specified in prog.  With each pattern in prog there can be  an
       associated  action that will be performed when a line of a file matches
       the pattern.  The set of patterns may appear literally as prog, or in a
       file specified as -f prog.

       Files  are  read in order; if there are no files, the standard input is
       read.  The file name `-'	 means	the  standard  input.	Each  line  is
       matched	against the pattern portion of every pattern-action statement;
       the associated action is performed for each matched pattern.

       An input line is made up of fields separated  by	 white	space.	 (This
       default	can  be	 changed by using FS, as described below.)  The fields
       are denoted $1, $2, ... ; $0 refers to the entire line.

       A pattern-action statement has the form

	    pattern { action }

       A missing { action } means print the line;  a  missing  pattern	always
       matches.

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

	    if ( conditional ) statement [ else statement ]
	    while ( conditional ) statement
	    for ( expression ; conditional ; expression ) statement
	    break
	    continue
	    { [ statement ] ... }
	    variable = expression
	    print [ expression-list ] [ >expression ]
	    printf format [ , expression-list ] [ >expression ]
	    next # skip remaining patterns on this input line
	    exit # skip the rest of the input

       Statements are terminated by semicolons, new lines or right braces.  An
       empty  expression-list  stands for the whole line.  Expressions take on
       string or numeric values as appropriate, and are built using the opera‐
       tors  +,	 -, *, /, %,  and concatenation (indicated by a blank).	 The C
       operators ++, --, +=, -=, *=, /=, and %= are also available in  expres‐
       sions.	Variables  may	be  scalars,  array elements (denoted x[i]) or
       fields.	Variables are initialized to  the  null	 string.   Array  sub‐
       scripts	may  be any string, not necessarily numeric; this allows for a
       form of associative memory.  String constants are quoted "...".

       The print statement prints its arguments on the standard output (or  on
       a file if >file is present), separated by the current output field sep‐
       arator, and terminated by the output record separator.	The  statement
       formats	its  expression	 list  according  to  the format.  For further
       information, see

       The built-in function length returns the length of its  argument	 taken
       as  a  string,  or  of  the  whole line if no argument.	There are also
       built-in functions exp, log, sqrt, and int.   The  last	truncates  its
       argument	 to  an integer.  substr(s, m, n) returns the n-character sub‐
       string	of   s	 that	begins	 at   position	 m.    The    function
       sprintf(fmt, expr, expr, ...)  formats the expressions according to the
       format given by fmt and returns the resulting string.

       Patterns are arbitrary Boolean combinations (!, ||, &&,	and  parenthe‐
       ses)  of	 regular  expressions  and  relational	expressions.   Regular
       expressions must be surrounded by slashes and are as  in	 egrep.	  Iso‐
       lated regular expressions in a pattern apply to the entire line.	 Regu‐
       lar expressions may also occur in relational expressions.

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

       A relational expression is one of the following:

	    expression matchop regular-expression
	    expression relop expression

       where a relop is any of the  six	 relational  operators	in  C,	and  a
       matchop	is  either  ~  (for contains) or !~ (for does not contain).  A
       conditional is an arithmetic expression, a relational expression, or  a
       Boolean combination 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 must  be
       the first pattern, END the last.

       A single character c may be used to separate the fields by starting the
       program with

	    BEGIN { FS = "c" }

       or by using the -Fc option.

       Other variable names with special meanings include NF,  the  number  of
       fields  in  the	current	 record; NR, the ordinal number of the current
       record; FILENAME, the name of the current input file; OFS,  the	output
       field  separator	 (default  blank);  ORS,  the  output record separator
       (default new line); and OFMT, the output format	for  numbers  (default
       "%.6g").

Options
       -	 Used for standard input file.

       -Fc	 Sets interfield separator to named character.

       -fprog	 Uses prog file for patterns and actions.

Examples
       Print lines longer than 72 characters:
	    length > 72

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

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

       Print fields in reverse order:
	    { for (i = NF; i > 0; --i) print $i }

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

       Print all lines whose first field is different from previous one:
	    $1 != prev { print; prev = $1 }

Restrictions
       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.

See Also
       lex(1), sed(1)
       "Awk - A Pattern Scanning and Processing Language" ULTRIX Supplementary
       Documents Vol. II: Programmer

									awk(1)
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