in reply to Regex to take an ip address before a comma

Assigns everything up to the first comma to $first: 

my ($first) = $str =~ /(.*?),/;

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Not as efficient, but possibly more readable: 

my ($first) = split(/,\s*/, $str);

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Update: D'oh! Fixed bug mentioned in reply.

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Re^2: Regex to take an ip address before a comma
by moritz (Cardinal) on Nov 25, 2008 at 15:49 UTC
    Assigns everything up to the first comma to $first
    $ perl -wle 'my $str = "a, b,"; my ($first) = $str =~ /(.*),/; print $
+first'
a, b

    [download]
    Up to the last comma, actually. If you want "up to the first comma" either use ([^,]*), or (.*?),
[reply]
[d/l]
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Re^2: Regex to take an ip address before a comma
by linuxer (Curate) on Nov 25, 2008 at 16:30 UTC

    I think the split() solution is more efficient than the regex solution.

    Tested with Perl 5.8.8 (ActiveState on WinXP)

    #!/usr/bin/perl
use strict;
use warnings;
use Benchmark qw( cmpthese );

my $str = ( ('X'x15) . ',' ) x 3;

cmpthese(
    -1,
    {
        # using regex
        's///' => sub {
            my ( $first ) = $str =~ m/(.*?),/;
        },
        # using split without limit
        'split_unl' => sub {
            my ( $first ) = split( m/,/, $str );
        },
        # using split with limit
        'split_lim' => sub {
            my ( $first ) = split( m/,/, $str, 2 );
        },
        # using split with limit and slice for scalar assignment
        'split_lim_sca' => sub {
            my $first = ( split( m/,/, $str, 2 ) )[0];
        },
    }
)

    [download]

    my result:

                      Rate          s///     split_lim     split_unl split
+_lim_sca
s///          577066/s            --          -13%          -13%      
+    -15%
split_lim     663032/s           15%            --           -0%      
+     -2%
split_unl     663629/s           15%            0%            --      
+     -2%
split_lim_sca 679348/s           18%            2%            2%      
+      --

    [download]

    Or did I miss something?

[reply]
[d/l]
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      and here's my result with a perl 5.10 (cygwin on same WinXP)

                        Rate          s///     split_lim     split_unl split
+_lim_sca
s///          288797/s            --          -12%          -12%      
+    -15%
split_lim     326805/s           13%            --           -1%      
+     -4%
split_unl     330050/s           14%            1%            --      
+     -3%
split_lim_sca 339541/s           18%            4%            3%      
+      --

      [download]
[reply]
[d/l]
        How can split which uses a regexp be faster than just a regexp? weird
[reply]
[d/l]

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