Re^2: Inserting a line in the middle of a text

That seems like a contortion to avoid opening an input filehandle and a separate output filehandle.

use strict;
use warnings;

my $filename = "inputfile.txt";
my $outputfile = $filename . "out";
my( $infh, $outfh );

open(  $infh, '<', $filename   ) or die $!;
open( $outfh, '>', $outputfile ) or die $!;

while( my $line = <$infh> ) {
    if( $line =~ /\bWilliam\b/i ) {
        print $outfh "Nick\n";
    }
    print $line;
}

close $infh  or die $!;
close $outfh or die $!;

rename $outputfile, $filename or die $!;
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This is pretty close to what the -i commandline switch does for Perl one liners, with the exception of the "-i.bak" behavior, which could easily be implemented here too.

This whole thing could be written as a one liner, by the way:

perl -pi.bak -e "/\bWilliam\b/i && print qq/Nick\n/;" filename.txt

Obviously I forgot the names you're searching on, but the principle works.

Dave

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Re^3: Inserting a line in the middle of a text by ikegami (Patriarch) on Jan 20, 2009 at 17:34 UTC
There are some advantages to working in-place over creating a temporary file: File permission and ownership is maintained. Using a temporary file requires more permissions. Using a temporary file may complicate the locking system required. Working in-place can be faster in some situations. This is pretty close to what the -i commandline switch does for Perl one liners `-i` is closer to `open(my $fh_in, '<', $qfn); unlink($qfn); open(my $fh_out, '>', $qfn); ...` [download] for now.	[reply] [d/l] [select]

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Re^3: Inserting a line in the middle of a text
by ikegami (Patriarch) on Jan 20, 2009 at 17:34 UTC

There are some advantages to working in-place over creating a temporary file:

File permission and ownership is maintained.
Using a temporary file requires more permissions.
Using a temporary file may complicate the locking system required.
Working in-place can be faster in some situations.

This is pretty close to what the -i commandline switch does for Perl one liners

-i is closer to

open(my $fh_in,  '<', $qfn);
unlink($qfn);
open(my $fh_out, '>', $qfn);
...
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for now.

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