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Full Discussion: Help in understanding awk expression
Top Forums Shell Programming and Scripting Help in understanding awk expression Post 302601317 by Corona688 on Thursday 23rd of February 2012 10:44:55 AM
Old 02-23-2012
Code:
# Before the program is run, set the variable n to the value "POINT"
-v n="POINT"

# For every line containing % somewhere:
'/%/ {
        # Print the entire line, followed by a newline, followed by "POINT"
        print $0 "\n" n
        # Skip this line so the '1' below doesn't print it
        next
# The '1' after the code block tells it to print every single line.
# It could be an expression too.
} 1' < file name

But I would've just written it as:

Code:
awk -v n="POINT" '/%/ { $0=$0"\n" n } 1'

To avoid the 'print' and the 'next'. For any line matching %, it just changes the current line( $0 ) to add "\nPOINT" to the end, so the print-every-line statement prints correctly in both cases.
This User Gave Thanks to Corona688 For This Post:
arun_maffy
 

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LEARN ABOUT DEBIAN

devel::trace

Trace(3pm)						User Contributed Perl Documentation						Trace(3pm)

NAME

       Devel::Trace - Print out each line before it is executed (like "sh -x")

SYNOPSIS

	 perl -d:Trace program

DESCRIPTION

       If you run your program with "perl -d:Trace program", this module will print a message to standard error just before each line is executed.
       For example, if your program looks like this:

	       #!/usr/bin/perl

	       print "Statement 1 at line 4
";
	       print "Statement 2 at line 5
";
	       print "Call to sub x returns ", &x(), " at line 6.
";

	       exit 0;

	       sub x {
		 print "In sub x at line 12.
";
		 return 13;
	       }

       Then  the "Trace" output will look like this:

	       >> ./test:4: print "Statement 1 at line 4
";
	       >> ./test:5: print "Statement 2 at line 5
";
	       >> ./test:6: print "Call to sub x returns ", &x(), " at line 6.
";
	       >> ./test:12:   print "In sub x at line 12.
";
	       >> ./test:13:   return 13;
	       >> ./test:8: exit 0;

       This is something like the shell's "-x" option.

DETAILS

       Inside your program, you can enable and disable tracing by doing

	   $Devel::Trace::TRACE = 1;   # Enable
	   $Devel::Trace::TRACE = 0;   # Disable

       or

	   Devel::Trace::trace('on');  # Enable
	   Devel::Trace::trace('off'); # Disable

       "Devel::Trace" exports the "trace" function if you ask it to:

	   import Devel::Trace 'trace';

       Then if you want you just say

	   trace 'on';		       # Enable
	   trace 'off'; 	       # Disable

TODO

       o   You should be able to  send the trace output to the filehandle of your choice.

       o   You should be able to specify the format of the output.

       o   You should be able to get the output into a string.

       We'll see.

LICENSE

       Devel::Trace 0.11 and its source code are hereby placed in the public domain.

Author
       Mark-Jason Dominus (C<mjd-perl-trace@plover.com>), Plover Systems co.  See the C<Devel::Trace.pm> Page at
       http://www.plover.com/~mjd/perl/Trace for news and upgrades.

perl v5.14.2							    2012-02-16								Trace(3pm)
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