Execute regexp on directory tree

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

I'm trying to exec regexp on directory tree using folowing script, but substitution regexp doesn't allow me to use \1 or $1 as parameter, so following example doesn't work.

#!/usr/bin/perl

use    warnings;
use    strict;
use    File::Find;

my $base = "C:\\Projects\\test";
my $ext = qr/.cpp$/;
my $regexp = qr/throw "(.+)"/;
my $substitute = qq{throw \("$1"\)};

find(\&process, $base);

# Collect files matching pre-set extension
sub    process {
        /$ext/ or return;
        my ($line, $file);

        $file =    $File::Find::name;
        $file =~ s{/}{\\}g;

        open (IN, '<', $file) or die "Can not open $file: $!";
        while (defined($line = <IN>)) {
            next if $line !~ /$regexp/;    
            chomp $line;
            print "$file:\n\t$line\n";
            $line =~ s/$regexp/$substitute/;
            print "\t$line\n";
        }
        close(IN);
}
[download]

Comment on Execute regexp on directory tree Download Code

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Re: Execute regexp on directory tree by Hofmator (Curate) on Dec 12, 2001 at 14:16 UTC
Your problem lies here: `my $substitute = qq{throw $"$1"$};` Using qq makes Perl interpolate variables which means that the current value of $1 (at this place undef) is inserted. Update: Well, typical, sorry, didn't double check what I wrote (and deleted now :). You have to use the following trick to achieve what you want: `my $substitute = q{qq{throw ("$1")}}; # and later substitute like this $line =~ s/$regex/$substitute/ee;` [download] The reason for this is that perl is not automatically doing an interpolation on the substitution string you insert. You have to force that by evalutating before substitution. -- Hofmator	[reply] [d/l] [select]
Re: Re: Execute regexp on directory tree by karmas (Sexton) on Dec 12, 2001 at 16:02 UTC
I tried to make changes you proposed, but, it didn't work: instead of `s/throw "[^"]+"/throw ($1)/` [download] The result semms like using: `s/throw "[^"]+"/throw (\$1)/` [download] So no substitution using matched values is performed, I guess I need that substitution regexp operator would evaluate the $substitute, whereas now it doesn't and just replaces using literal value. P.S. Anarion's suggestion also didn't work for me: `C:\Projects\Config2\9XImage.cpp: throw "Error writing to floppy!"; qq<throw ("$1")>` [download] Also literal evaluation.	[reply] [d/l] [select]
Re: Execute regexp on directory tree by Anarion (Hermit) on Dec 12, 2001 at 14:41 UTC
If you want to replace for the content of $1 you must use /ee modifier to the regex. `$line =~ s/$regexp/$substitute/ee;` [download] One advice, its better to use a negated character class: `qr/throw "([^"]+)"/;` [download] Update I forgot to say that then you have to change the substitution pattern to something to be evaluated: `my $substitute = q{qq<throw ("$1")>};` [download] $anarion=\$anarion; s==q^QBY_^=,$_^=$[x7,print	[reply] [d/l] [select]