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conditional replace using Perl

Posted on 2009-03-30
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Last Modified: 2012-05-06
I have a body of text and I want to do a conditional replace based, I am assuming with an if statement.

text example:  So I want to replace part of line 3, the attribute name, which is  "Significance", with a concatenation of line 1 value, in this case, "AtPID LR score" + "Significance".  How do I do this?

line1 <attr name= "mref" value = "AtPID LR score" index = "0" />
line 2<attr name= "Method" value = "AtPID LR score"  index = "0" />
line 3 <attr name= "Significance" value = "1248.12"  index = "0"/>
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Question by:MichelleLacy
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4 Comments
 
LVL 39

Assisted Solution

by:Adam314
Adam314 earned 500 total points
ID: 24020464

while(<>) {
    if($. == 1) {my $value = /value\s*=\s*"(.*?)"/;}
    elsif($. == 3) {s/name\s*=\s*"(.*?)"/name="$value$1"/;}
}

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Author Comment

by:MichelleLacy
ID: 24020612
I am very new to perl, so would you walk me through this a little.
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LVL 39

Accepted Solution

by:
Adam314 earned 500 total points
ID: 24020734
What I gave was the code to do what you asked - it is not a complete perl program.  Below is a complete program.  Save it to a file.  If you are on windows, it will have to have a ".pl" extension.  On unix, it can be named whatever you want.

To use it, pass the name of the input file on the command line.  Redirect the output to the new file.

For example, if you saved the below code to "dorename.pl", your original file was input.txt, and you wanted to have your new file named "output.txt", you would use this command:
    dorename.pl input.txt > output.txt

#!/usr/bin/perl
use strict;
use warnings;
 
my $value;
while(<>) {
    if($. == 1) {$value = /value\s*=\s*"(.*?)"/;}
    elsif($. == 3) {s/name\s*=\s*"(.*?)"/name="$value$1"/;}
    print;
}

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Author Closing Comment

by:MichelleLacy
ID: 31564396
thank you.  I used it right away, but forgot to close the session.
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