Regex to get everything before first /

[limzz]

Please help, I've spent over an hour trying to figure out how to take everything before the first forward slash in a string. It's consuming my sanity and I don't think I or my monitor will survive much longer.

(my $stuff) = ($thing =~ /^(\S+)\/*?/)

I've tried every variation on that line I can think of and none of them worked. Someone please save me before I lose my mind.

[toolic]

How's this:

use warnings;
use strict;

my $thing = 'foo/bar/goo';
(my $stuff) = ($thing =~ /^([^\/]+)/);
print "$stuff\n";

__END__

foo

[limzz]

I love you.

[davido]

toolic hit the nail on the head, but you might choose a different delimiter so that it wouldn't be necessary to escape the forward slash, like this:

my $thing = 'foo/bar/goo';
( my $stuff ) = ( $thing =~ 
    m{                # Quote-like characters are now {}.
        ^             # Match at the start of the string.
        ( [^/]+ )     # Capture everything in the set of all
                      # characters that are not '/'
    }x                # Close the regexp. x modifier allows
                      # freeform (as in non-significant
                      # whitespace).
);
print "$stuff\n";

The m{} brackets avoid the leaning toothpick syndrome in the original regexp. Of course if you were matching against a curly bracket the curly brackets wouldn't be all that wonderful as quote delimiters, but for this regexp they work out well. /x modifier added to allow comments and insignificant whitespace (it makes everything prettier).

[JavaFan]

/x modifier added to allow comments and insignificant whitespace (it makes everything prettier).

And it's easy to get carry it too far. I find /([^\/]*)/ far superior to your novella.

There's a guide line to not overdo comments. That's, don't do:

    $i++;   # Increment $i by one, or to the next "word".

That holds for patterns as well.

[davido]

I see a difference between explaining what I'm doing to someone who was having difficulty with a fairly straightforward regexp, in the context of a learning environment, and producing clear, concise, readable code in a non-instructional environment. A novella to an experienced user may be useful guidance to someone with less familiarity on the topic.

It could also be said that YAPE::Regex::Explain produces too much explanation. Yet when it's requested, it's available. Should someone comment the trivial in a normal script (whatever normal means)? No. Could excessive comments be helpful in the context of describing how a specific segment of code works to someone who has requested instruction? Yes.

Anyway, the code and comments were provided with the intent of being helpful, and I believe that goal was probably accomplished.

[wind]

One final addition to toolic and davido's posts:

You might as well make it match {0,} instead of {1,} so that strings that start with / will equal the empty string instead of undef.

This way you can avoid "Use of uninitialized value in concatenation (.)" warnings.

use warnings;
use strict;

my $thing = 'foo/bar/goo';
my ($stuff) = $thing =~ m{^([^/]*)};
print "$stuff\n";

__END__

foo

[ikegami]

my ($stuff) = $thing =~ m{^([^/]*)};

my ($stuff) = $thing =~ m{^(.*?)/}s;

my ($stuff) = split(qr{/}, $thing, 2);

my ($stuff) = split(qr{/}, $thing);

The second requires the presence of a "/", and uses the non-greedy modifier which I prefer to avoid.

[FunkyMonk]

the non-greedy modifier which I prefer to avoid

For what reason(s)?

[ikegami]

It fails poorly when there's a problem because the /.*?/ in /.*?// can match "/". It's only indirectly through co-operation with the rest of the pattern that it might be prevented from doing so. I prefer being more direct and explicitly prevent what should not be matched from matching.

[jwkrahn]

Another one:

my ($stuff) = $thing =~ m{[^/]*}g;

[planetscape]

See also: My Favourite Regex Tools