find and replace

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi, I am, at the moment, braindead. I have a little script that goes through a text file, finds a line w/ a string, then copies the entire line w/ the replaced string to another text file. But now I need to just *replace* the string, and I am definitely missing something:

use strict;
open (FILE ,"c:/index.htm");

for my $line (<FILE>) {
    if ($line =~ /foo/) {
        $line =~ s/foo/bar/gms;        
        print FILE "$line"; #obviously doesn't work
        print $line;
    }
    
}
close FILE;
[download]

the finding works fine, adn the replacing works fine *in memory*, but how do I replace the entire line (or just the string, same thing) in the original file? Many thanks, -John

Comment on find and replace Download Code

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Re: find and replace by JediWizard (Deacon) on Jun 21, 2005 at 15:05 UTC
try: `perl -pi -e 's/foo/bar/gms' File.txt` [download] And see perlrun, to understand the flags -p, -i, and -e They say that time changes things, but you actually have to change them yourself. —Andy Warhol	[reply] [d/l]
Re: find and replace by goober99 (Scribe) on Jun 21, 2005 at 15:09 UTC
A simple way to do this would be to use Tie::File. It is one of the core modules in the Perl distribution, so you would not have to install anything extra. Here is a snippet from a script I wrote using Tie::File: `tie @ThisFile, 'Tie::File', 'c:/index.html'; foreach(@ThisFile) {s/$SearchText/$ReplaceText/g}; untie @ThisFile;` [download]	[reply] [d/l]
Re^2: find and replace by Anonymous Monk on Jun 21, 2005 at 15:26 UTC
thanks, this works great.	[reply]
Re: find and replace by ambrus (Abbot) on Jun 21, 2005 at 15:17 UTC
Either you want inplace edit with the `$^I` variable; or write the results to a temporary file created with `File::Temp::tempfile` and then rename the new file to the original one. Here's an example for the second one: `use warnings; use strict; use File::Temp "tempfile"; my $i = "yourfile.txt"; # filename my ($O, $o) = tempfile; open my $I, $i or die "open: $!"; while (<$I>) { s/foo/bar/g; print $O $_; } close $O or die; rename $o, $i; __END__` [download]	[reply] [d/l] [select]
Re: find and replace by tlm (Prior) on Jun 21, 2005 at 15:53 UTC
Just for completeness, here's an example of one of the approaches that ambrus already mentioned: `{ local $^I = ''; local @ARGV = 'c:/index.htm'; while ( <> ) { s/foo/bar/g; print; } }` [download] I think that Tie::File rocks, but it's more firepower than the problem requires, I think. Also, why the `/m` in your `s///`, when there is no `^` or `$` in the regex? Likewise, why the `/s` when there is no `.` in the regex? the lowliest monk	[reply] [d/l]
Re: find and replace by GrandFather (Saint) on Jun 21, 2005 at 20:43 UTC
As an aside, if you are editing HTML be very very carefull. You should investigate the various `HTML::...` modules available on CPAN. Perl is Huffman encoded by design.	[reply] [d/l]