Top Forums Shell Programming and Scripting Don't understand how RS functions in awk Post 302449029 by joe228 on Friday 27th of August 2010 11:31:47 PM
Don't understand how RS functions in awk

I learn using RS in awk to extract portion of file in this forum which is wonderful solution to the problem. However, I don't understand how exactly it operates.

I don't quite understand the mechanism behind how searching for /DATA2/ can result in extracting the whole section under "DATA2"

sample
=====
Code:
DATA1
data11
data12

DATA2
data21
data22

DATA3
data31
data32

Code:
$cat sample | awk 'BEGIN {RS=""} /DATA2/'
DATA2
data21
data22

Since RS is set to be empty string, so each line now should be regarded as a field and so I expected printing $1 and $2 would give me the output of DATA1 and data11 but it didn't. Instead, it returned me with what is shown below:

Code:
$ cat sample | awk 'BEGIN {RS=""} { print $1 }'
DATA1
DATA2
DATA3
$ cat sample | awk 'BEGIN {RS=""} { print $2 }'
data11
data21
data31

So, can someone explain to me why it behaved this way?? Thanks!


Moderator's Comments:
Mod Comment Please use code tags, thank you!

Last edited by Franklin52; 08-28-2010 at 10:14 AM..
 
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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). ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +--------------------+-----------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +--------------------+-----------------+ |Availability | SUNWgawk | +--------------------+-----------------+ |Interface Stability | Volatile | +--------------------+-----------------+ NOTES
Source for gawk is available on http://opensolaris.org. Free Software Foundation Nov 3 1999 IGAWK(1)

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