Difference between revisions of "Regular Expressions"
Jump to navigation
Jump to search
(→Perl) |
|||
Line 11: | Line 11: | ||
|^||Start of string||$||End of string | |^||Start of string||$||End of string | ||
|- | |- | ||
− | |*||0 or more matches of previous expression | + | |*||0 or more matches of previous expression||( )||Subexpression |
|- | |- | ||
− | |<nowiki>+</nowiki>||1 or more matches of previous expression | + | |<nowiki>+</nowiki>||1 or more matches of previous expression||[ ]||Match anything between the [ ].<br>^as first character negates the match |
|- | |- | ||
− | |<nowiki>?</nowiki>||0 or 1 matches | + | |<nowiki>?</nowiki>||0 or 1 matches of previous expression.<br>Stop search as soon as next expression is found (non greedy) |
− | as soon as next expression is found (non greedy) | ||
|} | |} | ||
Line 32: | Line 31: | ||
:The string preceding whatever was matched by the last pattern match, not counting patterns matched in nested blocks that have been exited already. | :The string preceding whatever was matched by the last pattern match, not counting patterns matched in nested blocks that have been exited already. | ||
;$' | ;$' | ||
− | :The string following whatever was matched by the last pattern match, not counting patterns matched in nested blocks that have been exited already. | + | :The string following whatever was matched by the last pattern match, not counting patterns matched in nested blocks that have been exited already.<br>Example: |
<syntaxhighlight lang=perl> | <syntaxhighlight lang=perl> | ||
$_ = 'abcdefghi'; | $_ = 'abcdefghi'; | ||
/def/; | /def/; | ||
− | print "$`:$&:$' | + | print "$`:$&:$'"; |
# prints abc:def:ghi | # prints abc:def:ghi | ||
</syntaxhighlight> | </syntaxhighlight> | ||
+ | |||
+ | ;$1 | ||
+ | :String matched by the first subexpression. | ||
;$+ | ;$+ | ||
− | :The last bracket matched by the last search pattern. This is useful if you don't know which of a set of alternative patterns matched. | + | :The last bracket matched by the last search pattern. This is useful if you don't know which of a set of alternative patterns matched.<br>Example: |
<syntaxhighlight lang=perl> | <syntaxhighlight lang=perl> | ||
/Version: (.*)|Revision: (.*)/ | /Version: (.*)|Revision: (.*)/ |
Revision as of 10:00, 14 March 2018
. | Any character except newline | \c | Control character |
\d | Digit | \D | non Digit |
\s | Whitespace | \S | non Whitespace |
\w | Word character [A-Za-z0-9] | \W | non Word character |
^ | Start of string | $ | End of string |
* | 0 or more matches of previous expression | ( ) | Subexpression |
+ | 1 or more matches of previous expression | [ ] | Match anything between the [ ]. ^as first character negates the match |
? | 0 or 1 matches of previous expression. Stop search as soon as next expression is found (non greedy) |
Perl
- $var =~ /<pattern>/
- Generic syntax, this expression is true if the pattern is matched in $var
Following variables are when a match is made:
- $&
- Contains the string matched by the last pattern match
- $`
- The string preceding whatever was matched by the last pattern match, not counting patterns matched in nested blocks that have been exited already.
- $'
- The string following whatever was matched by the last pattern match, not counting patterns matched in nested blocks that have been exited already.
Example:
$_ = 'abcdefghi';
/def/;
print "$`:$&:$'";
# prints abc:def:ghi
- $1
- String matched by the first subexpression.
- $+
- The last bracket matched by the last search pattern. This is useful if you don't know which of a set of alternative patterns matched.
Example:
/Version: (.*)|Revision: (.*)/
&& ($rev = $+);