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Diffstat (limited to 'pod/perlfaq6.pod')
| -rw-r--r-- | pod/perlfaq6.pod | 38 |
1 files changed, 19 insertions, 19 deletions
diff --git a/pod/perlfaq6.pod b/pod/perlfaq6.pod index cf3a8fb7ca..9bbf80a018 100644 --- a/pod/perlfaq6.pod +++ b/pod/perlfaq6.pod @@ -1,6 +1,6 @@ =head1 NAME -perlfaq6 - Regular Expressions ($Revision: 1.18 $, $Date: 2002/10/30 18:44:21 $) +perlfaq6 - Regular Expressions ($Revision: 1.20 $, $Date: 2003/01/03 20:05:28 $) =head1 DESCRIPTION @@ -8,7 +8,7 @@ This section is surprisingly small because the rest of the FAQ is littered with answers involving regular expressions. For example, decoding a URL and checking whether something is a number are handled with regular expressions, but those answers are found elsewhere in -this document (in L<perlfaq9>: ``How do I decode or create those %-encodings +this document (in L<perlfaq9>: ``How do I decode or create those %-encodings on the web'' and L<perlfaq4>: ``How do I determine whether a scalar is a number/whole/integer/float'', to be precise). @@ -143,16 +143,16 @@ Here's another example of using C<..>: # now choose between them } continue { reset if eof(); # fix $. - } + } =head2 I put a regular expression into $/ but it didn't work. What's wrong? -As of Perl 5.8.0, $/ has to be a string. This may change in 5.10, +Up to Perl 5.8.0, $/ has to be a string. This may change in 5.10, but don't get your hopes up. Until then, you can use these examples if you really need to do this. -Use the four argument form of sysread to continually add to -a buffer. After you add to the buffer, you check if you have a +Use the four argument form of sysread to continually add to +a buffer. After you add to the buffer, you check if you have a complete line (using your regular expression). local $_ = ""; @@ -162,11 +162,11 @@ complete line (using your regular expression). # do stuff here. } } - + You can do the same thing with foreach and a match using the c flag and the \G anchor, if you do not mind your entire file being in memory at the end. - + local $_ = ""; while( sysread FH, $_, 8192, length ) { foreach my $record ( m/\G((?s).*?)your_pattern/gc ) { @@ -201,7 +201,7 @@ And here it is as a subroutine, modeled after the above: my $mask = uc $old ^ $old; uc $new | $mask . - substr($mask, -1) x (length($new) - length($old)) + substr($mask, -1) x (length($new) - length($old)) } $a = "this is a TEsT case"; @@ -280,8 +280,8 @@ documented in L<perlre>. No matter which locale you are in, the alphabetic characters are the characters in \w without the digits and the underscore. As a regex, that looks like C</[^\W\d_]/>. Its complement, -the non-alphabetics, is then everything in \W along with -the digits and the underscore, or C</[\W\d_]/>. +the non-alphabetics, is then everything in \W along with +the digits and the underscore, or C</[\W\d_]/>. =head2 How can I quote a variable to use in a regex? @@ -442,9 +442,9 @@ playing hot potato. Use the split function: while (<>) { - foreach $word ( split ) { + foreach $word ( split ) { # do something with $word here - } + } } Note that this isn't really a word in the English sense; it's just @@ -478,7 +478,7 @@ in the previous question: If you wanted to do the same thing for lines, you wouldn't need a regular expression: - while (<>) { + while (<>) { $seen{$_}++; } while ( ($line, $count) = each %seen ) { @@ -500,12 +500,12 @@ The following is extremely inefficient: @popstates = qw(CO ON MI WI MN); while (defined($line = <>)) { for $state (@popstates) { - if ($line =~ /\b$state\b/i) { + if ($line =~ /\b$state\b/i) { print $line; last; } } - } + } That's because Perl has to recompile all those patterns for each of the lines of the file. As of the 5.005 release, there's a much better @@ -602,7 +602,7 @@ still need the C<g> flag. { print "Found $1\n"; } - + After the match fails at the letter C<a>, perl resets pos() and the next match on the same string starts at the beginning. @@ -648,7 +648,7 @@ which works in 5.004 or later. For each line, the PARSER loop first tries to match a series of digits followed by a word boundary. This match has to start at the place the last match left off (or the beginning -of the string on the first match). Since C<m/ \G( \d+\b +of the string on the first match). Since C<m/ \G( \d+\b )/gcx> uses the C<c> flag, if the string does not match that regular expression, perl does not reset pos() and the next match starts at the same position to try a different @@ -737,7 +737,7 @@ Goldberg: (?:[A-Z][A-Z])*? GX /x; - + This succeeds if the "martian" character GX is in the string, and fails otherwise. If you don't like using (?!<), you can replace (?!<[A-Z]) with (?:^|[^A-Z]). |