Jump to content

Perl Programming/Regular expressions reference

    Add links
    From Wikibooks, open books for an open world
    < Perl Programming
    (Redirected from Perl Programming/Regular Expressions Reference)
    This page may need to be reviewed for quality.
    Previous: Regular expression operatorsIndexNext: Code reuse (modules)

    Regular expressions with Perl examples

    [edit | edit source]
    Metacharacter Description Example
    Note that all the if statements return a TRUE value
    .Matches an arbitrary character, but not a newline. 
    $string1 = "Hello World\n"; if ($string1 =~ m/...../) { print "$string1 has length >= 5\n"; }
    ( )Groups a series of pattern elements to a single element. When you match a pattern within parentheses, you can use any of $1, $2, …$9 later to refer to the previously matched pattern.

    Program:

    $string1 = "Hello World\n"; if ($string1 =~ m/(H..).(o..)/) { print "We matched '$1' and '$2'\n"; }

    Output:

    We matched 'Hel' and 'o W';
    +Matches the preceding pattern element one or more times. 
    $string1 = "Hello World\n"; if ($string1 =~ m/l+/) { print "There are one or more consecutive l's in $string1\n"; }
    ?Matches zero or one times. 
    $string1 = "Hello World\n"; if ($string1 =~ m/H.?e/) { print "There is an 'H' and a 'e' separated by "; print "0-1 characters (Ex: He Hoe)\n"; }
    ?Matches the *, +, or {M,N}'d regexp that comes before as few times as possible. 
    $string1 = "Hello World\n"; if ($string1 =~ m/(l+?o)/) { print "The non-greedy match with one or more 'l' print "followed by an 'o' is 'lo', not 'llo'.\n"; }
    *Matches zero or more times. 
    $string1 = "Hello World\n"; if ($string1 =~ m/el*o/) { print "There is an 'e' followed by zero to many"; print "'l' followed by 'o' (eo, elo, ello, elllo)\n"; }
    {M,N}Denotes the minimum M and the maximum N match count. 
    $string1 = "Hello World\n"; if ($string1 =~ m/l{1,2}/) { print "There exists a substring with at least one"; print "and at most two l's in $string1\n"; }
    [...]Denotes a set of possible matches. 
    $string1 = "Hello World\n"; if ($string1 =~ m/[aeiou]+/) { print "$string1 contains a one or more"; print "vowels\n"; }
    [^...]Matches any character not in the square brackets. 
    $string = "Sky."; if (String =~ /[^aeiou]/) { print "$string doesn't contain any vowels"; }
    |Matches one of the left or right operand. 
    $string1 = "Hello World\n"; if ($string1 =~ m/(Hello|Hi)/) { print "Hello or Hi is "; print "contained in $string1"; }
    \bMatches a word boundary. 
    $string1 = "Hello World\n"; if ($string1 =~ m/ello?\b/) { print "There is a word that ends with"; print " 'ello'\n"; } else { print "There are no words that end with"; print "'ello'\n"; }
    \wMatches alphanumeric, including "_". 
    $string1 = "Hello World\n"; if ($string1 =~ m/\w/) { print "There is at least one alpha-"; print "numeric char in $string1 (A-Z, a-z, 0-9, _)\n"; }
    \WMatches a non-alphanumeric character. 
    $string1 = "Hello World\n"; if ($string1 =~ m/\W/) { print "The space between Hello and "; print "World is not alphanumeric\n"; }
    \sMatches a whitespace character (space, tab, newline, formfeed) 
    $string1 = "Hello World\n"; if ($string1 =~ m/\s.*\s/) { print "There are TWO whitespace "; print "characters separated by other characters in $string1"; }
    \SMatches anything but a whitespace. 
    $string1 = "Hello World\n"; if ($string1 =~ m/\S.*\S/) { print "There are TWO non-whitespace "; print "characters separated by other characters in $string1"; }
    \dMatches a digit, same as [0-9]. 
    $string1 = "99 bottles of beer on the wall."; if ($string1 =~ m/(\d+)/) { print "$1 is the first number in '$string1'\n"; } '''Output:''' 99 is the first number in '<tt>99 bottles of beer on the wall.</tt>'
    \DMatches a non-digit. 
    $string1 = "Hello World\n"; if ($string1 =~ m/\D/) { print "There is at least one character in $string1"; print "that is not a digit.\n"; }
    ^Matches the beginning of a line or string. 
    $string1 = "Hello World\n"; if ($string1 =~ m/^He/) { print "$string1 starts with the characters 'He'\n"; }
    $ Matches the end of a line or string. 
    $string1 = "Hello World\n"; if ($string1 =~ m/rld$/) { print "$string1 is a line or string"; print "that ends with 'rld'\n"; }
    Previous: Regular expression operatorsIndexNext: Code reuse (modules)
    Retrieved from "https://en.wikibooks.org/wiki/Perl_Programming/Regular_expressions_reference"
    close