TRIM in Perl?

peacemaker1820 has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: TRIM in Perl? by jmcnamara (Monsignor) on Sep 10, 2002 at 14:05 UTC
That removes the leading spaces but not the trailing spaces. There isn't a built in trim function but japhy wrote a nice one: trim() magic You will find a discussion on this in perlfaq4 How do I strip blank space from the beginning/end of a string?. -- John.	[reply]
Re: TRIM in Perl? by samurai (Monk) on Sep 10, 2002 at 15:36 UTC
No, that will NOT drop the leading and trailing spaces. Only the leading spaces (you are anchored by "^"). There's no sub for trimming strings in perl. The best way is probably to just go ahead and bite the bullet: `my $temp = " Hello "; $temp =~ s/^\s+//; $temp =~ s/\s+$//;` [download] You can write your own trim() function to automate this if you wish. -- perl: code of the samurai	[reply] [d/l]
Re^2: TRIM in Perl? by Aristotle (Chancellor) on Sep 10, 2002 at 16:21 UTC
Occasionally also written as `s/^\s+\|\s+$//g;` Makeshifts last the longest.	[reply] [d/l]
Re: Re^2: TRIM in Perl? by samurai (Monk) on Sep 12, 2002 at 13:28 UTC
I did some benchmarking, and I am absopositively amazed at how much faster that is than two s//'s. 3-4 times faster in my tests. Thank you very much for that one. -- perl: code of the samurai	[reply]
Re: TRIM in Perl? by charnos (Friar) on Sep 10, 2002 at 16:31 UTC
~~Since with all the suggestions here we're just eliminating all spaces in the string, wouldn't simple transliteration (`$temp =~ tr/ //d;`) be faster/simpler?~~ Update: EEK! bangs head Nevermind, I retract that, `$temp =~ s/^\s+\|\s$/` would be the best way to do it.	[reply] [d/l] [select]
Re^2: TRIM in Perl? by Aristotle (Chancellor) on Sep 10, 2002 at 16:45 UTC
Where did you see "all suggestions [..] just eliminating all spaces"? None of them do. Makeshifts last the longest.	[reply]
Re: TRIM in Perl? by Rabenschwinge (Novice) on Jan 12, 2011 at 10:34 UTC
I have a problem with that one: `#!/usr/bin/env perl use strict; use warnings; my @strings = (' Test ', 'Test 2 ', ' A ', 'multi line string ',' '); foreach my $string (@strings) { $string =~ s/^\s+//m; $string =~ s/\s+$//m; print "'$string'\n"; }` [download] Returns: `'Test' 'Test 2' 'A' 'multi line string' ''` [download] That is almost correct, but it does remove a line break in the middle of the string it shouldn't: There should be two line breaks between "multi" and "line" but only one remains.	[reply] [d/l] [select]
Re^2: TRIM in Perl? by Corion (Patriarch) on Jan 12, 2011 at 10:43 UTC
Why do you add `/m` to your regular expressions? See perlop - `/m` changes the meaning of `$` and `^`.	[reply] [d/l] [select]
Re^2: TRIM in Perl? by Anonymous Monk on Jan 12, 2011 at 10:42 UTC
That is almost correct, but it does remove a line break in the middle of the string it shouldn't Who says it shouldn't? The OP wanted whitespaces removed, that is what \s means, whitespaces (\n, \r, \t, \f, and " ") Read more... (2 kB) New questions go in Seekers of Perl Wisdom (see Where should I post X?) , don't worry, yours will be moved there shortly	[reply] [d/l]
Re^2: TRIM in Perl? by Anonymous Monk on Feb 10, 2011 at 10:01 UTC
I wanted the same thing I think - remove leading and trailing space, on a per line basis, ignoring newlines. I've just done this and it seems to work, i.e. linecount remains same before and after. `cat test.dat \| perl -n -e 'chomp; s/^\s+//; s/\s+$//; print "$_\n";'` [download]	[reply] [d/l]