Re: Add a Line to a Text File

I got it, I hope someone also will be able to use this little silly script in their mundane tasks.

 use strict;
use warnings;

my $infile = $ARGV[0] or die "$0 Usage:\n\t$0 <input file>\n\n";
open(my $fd , '<' , $infile) or die "$0 Error: Couldn't open $infile f
+or reading: $!\n";

my $outfile = 'processedData.txt';
open(my $fh, '>', $outfile) or die "Could not open file '$outfile' $!"
+;

my $previous;
    print $fh "data\n";
while (<$fd>) {

    $previous = $_;
    print $fh $previous;
    
}
chomp($previous);
close $fh;
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Comment on Re: Add a Line to a Text File Download Code

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Re^2: Add a Line to a Text File
by Athanasius (Archbishop) on Aug 24, 2013 at 04:04 UTC

Hello xanadol, and welcome to the Monastery!

Glad to see you found the solution. For the record, this is an FAQ: How do I change, delete, or insert a line in a file, or append to the beginning of a file?.

Some observations on your code:

Great to see you useing strict and warnings!
The while loop can be written more idiomatically:

print $fh $_ while <$fd>;
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chomping $previous after the while loop does nothing.

If you want to prepend a line of text to an existing file in-place, you can use the core module Tie::File:

use strict;
use warnings;
use Tie::File;

my $file = $ARGV[0]                or die "$0 Usage:\n\t$0 <file>\n\n"
+;

tie my  @array, 'Tie::File', $file or die "Cannot tie file '$file': $!
+";
unshift @array, 'data';
untie   @array;
[download]

Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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