Re^4: header footer

So this is the one that i tried and it works. Thanks kenosis and others for taking the time.

#!/usr/bin/perl
use strict;
use warnings;

open FILE1,"input.txt";
open FILE2,">>output.txt";
foreach my $line ( <FILE1> )
{
$_= $line;
s/^HDR.{47}//;
s/\KFTR.{27}//;

print FILE2 $_;

}
close FILE1;
close FILE2;
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this made the most clarity for me. I am assuming that the entire file doesnt gets stored in the $_ in this approach, correct me if i am wrong. and the file is only getting read one line at a time. This i want to make sure so that it performs well when i actually test with the huge file.

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Re^5: header footer by Kenosis (Priest) on Mar 05, 2014 at 01:20 UTC
Consider the following instead: `use strict; use warnings; use autodie; open my $FILE1, '<', 'input.txt'; open my $FILE2, '>', 'output.txt'; while (<$FILE1>) { s/^HDR.{47}\|FTR.+//; print $FILE2 $_; } close $FILE1; close $FILE2;` [download] `autodie` will trap the file i/o errors (you're not handling these, but you should) Use only lexical (`my`) file handles Use `while` to iterate through the file The two substitutions were combined into one If `FTR` marks the footer to the end of the line, you can just use `FTR.+` to remove it, since in your example there were only 30 characters left--including `FTR`. However, it's certainly OK to use `FTR.{27}`, if you prefer.	[reply] [d/l] [select]

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Re^5: header footer
by Kenosis (Priest) on Mar 05, 2014 at 01:20 UTC

Consider the following instead:

use strict;
use warnings;
use autodie;

open my $FILE1, '<', 'input.txt';
open my $FILE2, '>', 'output.txt';

while (<$FILE1>) {
    s/^HDR.{47}|FTR.+//;
    print $FILE2 $_;
}

close $FILE1;
close $FILE2;
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autodie will trap the file i/o errors (you're not handling these, but you should)
Use only lexical (my) file handles
Use while to iterate through the file
The two substitutions were combined into one

If FTR marks the footer to the end of the line, you can just use FTR.+ to remove it, since in your example there were only 30 characters left--including FTR. However, it's certainly OK to use FTR.{27}, if you prefer.

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