Scott: Created page with '== Perl Regular Expressions == /a.c/ # (1 of any character) matches "abc" but not "ac" or "abbc" /a*c/ # (0 or more) matches "c", "ac", "aac", …'

2011-02-01T18:27:01Z

Created page with '== Perl Regular Expressions == <source lang="perl"> /a.c/ # (1 of any character) matches "abc" but not "ac" or "abbc" /a*c/ # (0 or more) matches "c", "ac", "aac", …'

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== Perl Regular Expressions ==
<source lang="perl">
/a.c/ # (1 of any character) matches "abc" but not "ac" or "abbc"
/a*c/ # (0 or more) matches "c", "ac", "aac", "aaac", but not "abc"
/a+c/ # (1 or more) matches "ac", "aac", "aaac", but not "abc" or "c"
/a?c/ # (0 or 1) matches "c" and "ac" but not "aac", "aaac" or "abc"
/a{2,3}c/ # (2 to 3) matches "aac" and "aaac" but not "ac"
/a{2,}c/ # (2 or more) matches "aac" and "aaaaaac" but not "ac"
/a{2}c/ # (2) matches "aac"
/a(bc)?d/ # matches "ad" and "abcd"
/a(bb|cc)d/ # matches "abbd" and "accd"
/a[bc]d/ # matches "abd" and "acd"
/a[0-9]+c/ # matches "a123c" but not "ac" or "a1b2c"
/a[^0-9]c/ # matches "abc" but not "ac" or "a1c"
\d matches a digit [0-9]
\w matches a word character [A-Za-z0-9_]
\s matches a whitespace character [\f\t\n\r ]
\D = [^\d], \W = [^\w], \S = [^\s]
/[\dA-Fa-f]+/ # matches hexadecimal numbers
m([\dA-Fa-f]+) # same, can enclose with arbitrary punctuation pairs
m{http://} # matches "http://"
/yes/i # (case insensitive) matches "yes", "Yes", and "YES"
/^>/ # match ">" character at beginning of line
/>$/ # match ">" character at end of line
/^abc$/ # only matches "abc"
/^\s*$/ # matches any line containing only whitespace
/\babc\b/ # (word boundary) matches "my abc" but not "abcd"
# (...) saves regular expression submatches to memory
$_ = "Hello there, neighbor";
if (/(\S+) (\S+), (\S+)/) {
print "words were $1 $2 $3\n";
}
# automatic match variables
# $` is everything before the match
# $& is the match itself
# $' is everthing after the match
if ("Hello there, neighbor" =~ /\s(\w+),/) {
print "words were $` $& $'\n";
}
my $string = "Here is my string.";
if ($string =~ /[Hh]ere/){...} # matches
# translate lowercase vowels to upper
$string =~ tr/aeiou/AEIOU/; # HErE Is my strIng.
# delete all whitespace (g means global)
$string =~ s/\s+//g; # HErEIsmystrIng.
if ($string =~ /[aeiou]/) {
print "Found lowercase vowels."
}
# may use non-slash delimiters
s{^https://}{http://}
</source>

== A Program for Testing Regular Expressions ==
<source lang="perl">
#!/usr/bin/perl
while (<>) { # take one input line at a time
chomp;
if (/YOUR_PATTERN_GOES_HERE/) {
print "Matched: |$`<$&>$'|\n"; # the special match vars
} else {
print "No match: |$_|\n";
}
}
</source>

== Uses for Regular Expressions ==
<source lang="perl">
@fields = split /:/, "abc:def:g:h"; # gives ("abc", "def", "g", "h")
@fields = split /\s+/, "I am a cow."; # gives ("I", "am", "a", "cow.")
@fields = split ' ', "I am a cow."; # gives ("I", "am", "a", "cow.")
my $sentence = join '_', @fields; # gives "I_am_a_cow."
</source>

Perl Regular Expressions - Revision history

Scott: Created page with '== Perl Regular Expressions == /a.c/ # (1 of any character) matches "abc" but not "ac" or "abbc" /a*c/ # (0 or more) matches "c", "ac", "aac", …'