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Full Discussion: awk variables in regex expression ?
Top Forums Shell Programming and Scripting awk variables in regex expression ? Post 302486124 by michaelrozar17 on Friday 7th of January 2011 04:48:10 AM
Old 01-07-2011
Quote:
Originally Posted by vilius
Hello,

Could someone explain why this one returns nothing:
Code:
$ x=/jon/
$ echo jon | awk -v xa=$x '$1~xa {print}'
$

When a pattern matching is done using ~ we need to give the reg-exp in between / / (2 forward slashes).Still, when given inside the slashes it is taken as literally, so when changing the above awk as
Code:
echo jon | awk -v xa=$x '$1~/xa/ {print}'

it matches the word xa and not the variable xa's value.Hence we need to expand the variable as below
Code:
x=/jon/
echo jon | awk -v xa=$x '$1~/'"$xa"'/ {print}'

This is not the case when == is used as you would know this is used to equate between variables.Therefore in code $1==xa.. xa is expanded (to jon).
 

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LEARN ABOUT SUSE

igawk

IGAWK(1)							 Utility Commands							  IGAWK(1)

NAME

       igawk - gawk with include files

SYNOPSIS

       igawk [ all gawk options ] -f program-file [ -- ] file ...
       igawk [ all gawk options ] [ -- ] program-text file ...

DESCRIPTION

       Igawk is a simple shell script that adds the ability to have ``include files'' to gawk(1).

       AWK programs for igawk are the same as for gawk, except that, in addition, you may have lines like

	      @include getopt.awk

       in your program to include the file getopt.awk from either the current directory or one of the other directories in the search path.

OPTIONS

       See gawk(1) for a full description of the AWK language and the options that gawk supports.

EXAMPLES

       cat << EOF > test.awk
       @include getopt.awk

       BEGIN {
	    while (getopt(ARGC, ARGV, "am:q") != -1)
		 ...
       }
       EOF

       igawk -f test.awk

SEE ALSO

       gawk(1)

       Effective AWK Programming, Edition 1.0, published by the Free Software Foundation, 1995.

AUTHOR

       Arnold Robbins (arnold@skeeve.com).

Free Software Foundation					    Nov 3 1999								  IGAWK(1)
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