After visiting this node I realized that I wasn't too sure when to use grep(1), perl, or perl's grep
Here are the results of my experiment: First I created a data file 
#!/usr/bin/perl -w

use strict;

my $a;
my $i;
open( OUT, ">data.txt" );
for( $i = 0; $i < 1000000; $i++ ) {
    $a = rand( 126 );
    $a = int( $a );
    until( $a > 33 ) {
        $a = rand( 126 );
        $a = int( $a );
    }

    print OUT chr( $a );
    print OUT "\n" if( $i % 80 == 0);
}
close( OUT );

[download]
Then I made some tests using the Benchmark module 
#!/usr/bin/perl

use Benchmark;

sub child_grepping {
    $a = `/bin/grep 'S;Dvg&T?sBu=\@j4qkP&O' data.txt`;
}

sub inline_grepping {
    open( IN, "data.txt" );
    @lines = <IN>;
    close( IN );

    ($a) = grep /S;Dvg&T\?sBu=\@j4qkP&O/, @lines;
}

sub child_perlizing {
    my $command = "perl -e 'while( \$line = <> ) { if( \$line =~ ";
    $command .= "/S;Dvg&T\\\?sBu=\\\@j4qkP&O/) { print \$line; last; }
+ }' ";
    $command .= '< data.txt';
    $a = `$command`;
}

sub inline_perlizing {
    my $line;
    open( IN, "data.txt" );
    while( $line = <IN> ) {
        if( $line =~ /S;Dvg&T\?sBu=\@j4qkP&O/ ) {
            $a = $line;
            last;
        }
    }
    close( IN );
}

timethese( 1000, { child_grepping   => 'child_grepping()',
                   child_perlizing  => 'child_perlizing()',
                   inline_grepping  => 'inline_grepping()',
                   inline_perlizing => 'inline_perlizing()' } );

[download]
And then when I ran my test I got some interesting results (this took a while btw ;) 
Benchmark: timing 1000 iterations of child_grepping, child_perlizing, 
  inline_grepping, inline_perlizing...
child_grepping: 
  15 wallclock secs ( 0.17 usr  0.62 sys +  7.27 cusr  7.17 csys =  0.
+00 CPU)
child_perlizing: 
  90 wallclock secs ( 0.17 usr  0.60 sys + 75.91 cusr  6.87 csys =  0.
+00 CPU)
inline_grepping: 
  191 wallclock secs (177.97 usr +  7.64 sys = 185.61 CPU)
inline_perlizing: 
  66 wallclock secs (59.68 usr +  1.19 sys = 60.87 CPU)

[download]
Can somebody help me analyze the results?

-- Dave

In reply to Groking grep by spaz

Title:
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