A quick benchmark shows that fgrep is even about three times as fast as perl. (For 5.10.0, that is — with 5.8.8, the ratio is even worse... considerably!)  Such a large difference is somewhat surprising (to me). I would've expected perl-5.10 to be about on par with fgrep. So, please, someone point out what I've done wrong in my benchmark... :)

perl-5.10.0: 

        Rate  perl fgrep
perl  30.8/s    --  -71%
fgrep  106/s  246%    --

[download]

perl-5.8.8: 

        s/iter     perl    fgrep
perl      9.38       --    -100%
fgrep 3.00e-04 3124967%       --

[download]

(In this particular reported case, none of the search words were found in $^X (the perl binary), so all strings had to be tested.) 

use strict;
use warnings;
use Benchmark qw(cmpthese);

my @letters = ('A'..'Z','a'..'z');

sub searchword {
    my $len = shift;
    return join '', map { @letters[int rand(@letters)] } 1..$len;
}

my @words = map { searchword(3+rand(20)) } 1..300;

my $strings_file = "list_of_strings_file";
open my $fh, ">", $strings_file or die "Couldn't write '$strings_file'
+: $!";
print $fh "$_\n" for @words;
close $fh;

my $re = join '|', @words;

cmpthese(100, {
    'perl' => sub {
        open my $fh, "<", $^X or die "Couldn't open '$^X': $!";
        my $content;
        sysread $fh, $content, 1e7 or die $!;
        close $fh;
        $content =~ /$re/;
    },
    'fgrep' => sub {
        system qw(grep -F -o -f), $strings_file, $^X;
    },
});

[download]

In reply to Re^2: Searching multiple expressions in multiple Files (perl-5.10 vs. fgrep) by almut
in thread Searching multiple expressions in multiple Files by technoz

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