r.joseph has asked for the wisdom of the Perl Monks concerning the following question:

Hey all. Suppose the string:  . . .Perlmonks  . . .is . .the . . . .coolest .place. Notice how each dot respresents a space (I did that for clarity, so that you could visualize multiple spaces (including leading spaces) - just realize that there can be any number of space between words).

I want to take the above string and turn it into: Perlmonks_is_the_coolest_place

Basically, replacing any number of spaces between words with ONE underscore. I tried:
$str =~ s/\s+/_/ig;

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but that replaces each space with an underscore. Removing the "g" modifier from the regex does (obviously) no good.

I realize that this will probably end up being a very simple solution, but I have been studying all day and my brain is fried, so please help a poor, brain-fried college student out? Thanks all!

r. j o s e p h
"Violence is a last resort of the incompetent" - Salvor Hardin, Foundation by Issac Asimov

Replies are listed 'Best First'.
Re: Replacing multiple spaces into one character?
by chromatic (Archbishop) on Oct 09, 2001 at 07:10 UTC
    tr/ /_/s;, as /s is for squash multiple.

    Doing it in one line while removing leading whitespace is trickier. There are several potentially nasty regular expressions. Just say no.

    Update: Squashing several expressions onto one line technically counts, but it wasn't what I meant, smart guy!

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[d/l]
      $str = '  say  as  simple  as  a   b   c  :-)  ';
$str =~ s/^\s+|\s+$//g, $str =~ tr/ /_/s, print $str;

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Re: Replacing multiple spaces into one character?
by John M. Dlugosz (Monsignor) on Oct 09, 2001 at 07:10 UTC
    Er, it works for me. To wit: 
    $str= "   perlmonks   is   the   coolest";
$str =~ s/\s+/_/g;
print $str;

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    prints: _perlmonks_is_the_coolest

    (I left out the i modifier because space is the same in capital or lower-case. I don't think that would change the behavior, though!)

    —John

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[d/l]
      Agreed, it works exactly as r.joseph presented it. However you may want to think about using 
      $str =~ s/ +/_/g;

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      instead, since it doesn't mess with your newline characters. That is, with your version "perl\n" becomes "perl_".

      - Boldra
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Re: Replacing multiple spaces into one character?
by Zaxo (Archbishop) on Oct 09, 2001 at 07:36 UTC

    This uses the magical whitespace arg to split:

    my $str = "  Perlmonks   is  the\tcoolest\n \tplace";
$str = join "_", split " ", $str;
print $str,$/;

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    The magic strips leading whitespace and is greedy about the rest. This is a little broader than you asked for, but still does what you want.

    After Compline,
    Zaxo

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Re: Replacing multiple spaces into one character?
by tachyon (Chancellor) on Oct 09, 2001 at 07:16 UTC

    Not recommended but TIMTOWTDI requires someone post this ;-) 

    $str ='   Perlmonks is     a      very    cool place  ';
$str = join '_', split /\s+/, $str;
print $str;

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    cheers

    tachyon

    s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

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[d/l]
      you could also use the magical ' ' (single space) arg to split, which will remove leading spaces as well... 
      #!/usr/bin/perl -wT
use strict;

my $str ='   Perlmonks is     a      very    cool place  ';
$str = join '_', split ' ', $str;
print $str, "\n";

=OUTPUT
Perlmonks_is_a_very_cool_place

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      -Blake

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[d/l]

        Thanks blakem that null string that you get using /\s+/is a pain. I never realised that ' ' was magical.

        cheers

        tachyon

        s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

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Re: Replacing multiple spaces into one character?
by pike (Monk) on Oct 09, 2001 at 11:22 UTC
    How about: 

    $str = '   xx  y    z  ';
$str =~ s/(?<=\w)\s+(?=\w)/g;  #replace only spaces between letters
$str=~ tr/ //d; #delete leading and trailing spaces

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    pike

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Re: Replacing multiple spaces into one character?
by thunders (Priest) on Oct 09, 2001 at 19:01 UTC 
    1 while $str =~ s/[ ]+/_/;

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    will also work for this one, it's similar to the /g modifier except that it re-evaluates the entire string after every substitution. But this is for entertainment TIMTOWTDI value only cause something like this 
    1 while $str =~ s/[ ]+/ _ /;

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    will just keep running forever as it tries to replace the spaces it creates.
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