Front page | perl.beginners |
Postings from January 2002
On Jan 30, ERIC Lawson - x52010 said:
>Why don't the match operators and regexps in the following produce the
>same results?
>
> if ($editbl =~ /^\S+$/) { print AFILE "$editbl\n"; }
> if ($editbl !~ /^\s*$/) { print EFILE "$editbl\n"; }
Your logic is off. The first regex says:
"If $editbl matches 'start of string' followed by 'one or more
non-whitespaces' followed by 'end of string' then print it to AFILE."
The second regex says:
"If $editbl does NOT match 'start of string' followed by 'zero or more
whitespaces' followed by 'end of string' then print it to EFILE."
Your second regex SHOULD be:
if ($editbl !~ /\s/) { ... }
because the synonym of "only non-whitespaces" is "not a single
whitespace". Actually, you need to be slightly more specific:
if (length($editbl) and $editbl !~ /\s/) { ... }
The problem with the logic of the second regex is that
"foo bar" =~ /^\S+$/
fails, while
"foo bar" !~ /^\s*$/
succeeds, since "foo bar" is certainly not made up solely of whitespace
characters.
--
Jeff "japhy" Pinyan japhy@pobox.com http://www.pobox.com/~japhy/
RPI Acacia brother #734 http://www.perlmonks.org/ http://www.cpan.org/
** Look for "Regular Expressions in Perl" published by Manning, in 2002 **
<stu> what does y/// stand for? <tenderpuss> why, yansliterate of course.
Thread Previous