From: PerlFAQ Server on 18 May 2010 00:00 This is an excerpt from the latest version perlfaq4.pod, which comes with the standard Perl distribution. These postings aim to reduce the number of repeated questions as well as allow the community to review and update the answers. The latest version of the complete perlfaq is at http://faq.perl.org . -------------------------------------------------------------------- 4.32: How do I strip blank space from the beginning/end of a string? (contributed by brian d foy) A substitution can do this for you. For a single line, you want to replace all the leading or trailing whitespace with nothing. You can do that with a pair of substitutions. s/^\s+//; s/\s+$//; You can also write that as a single substitution, although it turns out the combined statement is slower than the separate ones. That might not matter to you, though. s/^\s+|\s+$//g; In this regular expression, the alternation matches either at the beginning or the end of the string since the anchors have a lower precedence than the alternation. With the "/g" flag, the substitution makes all possible matches, so it gets both. Remember, the trailing newline matches the "\s+", and the "$" anchor can match to the physical end of the string, so the newline disappears too. Just add the newline to the output, which has the added benefit of preserving "blank" (consisting entirely of whitespace) lines which the "^\s+" would remove all by itself. while( <> ) { s/^\s+|\s+$//g; print "$_\n"; } For a multi-line string, you can apply the regular expression to each logical line in the string by adding the "/m" flag (for "multi-line"). With the "/m" flag, the "$" matches *before* an embedded newline, so it doesn't remove it. It still removes the newline at the end of the string. $string =~ s/^\s+|\s+$//gm; Remember that lines consisting entirely of whitespace will disappear, since the first part of the alternation can match the entire string and replace it with nothing. If need to keep embedded blank lines, you have to do a little more work. Instead of matching any whitespace (since that includes a newline), just match the other whitespace. $string =~ s/^[\t\f ]+|[\t\f ]+$//mg; -------------------------------------------------------------------- The perlfaq-workers, a group of volunteers, maintain the perlfaq. They are not necessarily experts in every domain where Perl might show up, so please include as much information as possible and relevant in any corrections. The perlfaq-workers also don't have access to every operating system or platform, so please include relevant details for corrections to examples that do not work on particular platforms. Working code is greatly appreciated. If you'd like to help maintain the perlfaq, see the details in perlfaq.pod.
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