Multiline search replace with Perl

Question

I know this kind of questions have been asked already many times before. The reason why I come here again is that I feel like I've missed something simple and fundamental.

Is it possible to make this kind of search-replace routine better. For example without opening same file twice. Also speed related advices are welcome.

Please notice that this works with multiline matches and replaces also multiline strings.

#!/bin/perl -w -0777

local $/ = undef;

open INFILE, $full_file_path or die "Could not open file. $!";
$string =  <INFILE>;
close INFILE;

$string =~ s/START.*STOP/$replace_string/sm;

open OUTFILE, ">", $full_file_path or die "Could not open file. $!";
print OUTFILE ($string);
close OUTFILE;

Answer 1

This kind of search and replace can be accomplished with a one-liner such as -

perl -i -pe 's/START.*STOP/replace_string/g' file_to_change

For more ways to accomplish the same thing check out this thread. To handle multi-line searches use the following command -

perl -i -pe 'BEGIN{undef $/;} s/START.*STOP/replace_string/smg' file_to_change

In order to convert the following code from a one-liner to a perl program have a look at the perlrun documentation.

If you really find the need to convert this into a working program then just let Perl handle the file opening/closing for you.

#!/usr/bin/perl -pi
#multi-line in place substitute - subs.pl
use strict;
use warnings;

BEGIN {undef $/;}

s/START.*STOP/replace_string/smg;

You can then call the script with the filename as the first argument

$perl subs.pl file_to_change

If you want a more meatier script where you get to handle the file open/close operations(don't we love all those 'die' statements) then have a look at the example in perlrun under the -i[extension] switch.