Edit a file in perl

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06-13-2014

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Edit a file in perl

Hi,

I have a file like

Code:

$ cat abc
HDR XXX
content XXX
content YYY
content XXX
content YYY
content XXX
content YYY
TRL YYY

I want to replace the lines staritng with HDR and TRL
For this I have written below code

Code:

#!/usr/bin/perl -w

use strict;

open ( FH , "+< abc" ) || die "Can't open abc $!";

while(<FH>){
        if (/^HDR/){
                s/XXX/YYY/; print FH;
        }elsif(/^TRL/){
                s/YYY/XXX/; print FH;
        }
}

close (FH);

However on runnig this I end up with something like

Code:

$ cat abc
HDR XXX
HDR YYY
XXX
content YYY
content XXX
content YYY
content XXX
content YYY
TRL YYY
TRL XXX

Help!!!
(answers in perl only)

sam05121988

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06-13-2014

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In your logic every line is printed, then some (starting with "HDR" or "TRL") are changed and then printed again.

You need to switch off the automatic echoing of lines, then move the "print FH" out of the if- and elsif-branches, like this:

Code:

while(<FH>){
        if (/^HDR/){
                s/XXX/YYY/;
        }elsif(/^TRL/){
                s/YYY/XXX/;
        }
        print FH;
}

I hope this helps.

bakunin

bakunin

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