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The regular expression (i.e. pattern) to be searched is placed after the first delimiting symbol (slash here) and the replacement follows the second symbol. Slash ( / ) is the conventional symbol, originating in the character for "search" in ed, but any other could be used to make syntax more readable if it does not occur in the pattern or ...
A regular expression (shortened as regex or regexp), [1] sometimes referred to as rational expression, [2] [3] is a sequence of characters that specifies a match pattern in text. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings , or for input validation .
A metacharacter is a character that has a special meaning to a computer program, such as a shell interpreter or a regular expression (regex) engine.. In POSIX extended regular expressions, there are 14 metacharacters that must be escaped — preceded by a backslash (\) — in order to drop their special meaning and be treated literally inside an expression: opening and closing square brackets ...
An early example is sed, where in the substitution command s/regex/replacement/ the default slash / delimiters can be replaced by another character, as in s,regex,replacement,. Constructor functions [ edit ]
Metacharacters are interpreted unless quoted by a backslash, double quotes, or square brackets. See the section on regex. The obvious example is, you must quote any slash in your pattern so it won't be interpreted as the closing slash delimiter, using \/ instead of / to match a literal slash. A regexp interprets all metacharacters.
Perl Compatible Regular Expressions (PCRE) is a library written in C, which implements a regular expression engine, inspired by the capabilities of the Perl programming language. Philip Hazel started writing PCRE in summer 1997. [3]
The slash is also used as the default regular expression delimiter, so to be used literally in the expression, it must be escaped with a backslash \, leading to frequent escaped slashes represented as \/. If doubled, as in URLs, this yields \/\/ for an escaped //.
For a cheat sheet on writing regexes, see Wikipedia:AutoWikiBrowser/Regular expression. For case insensitive searches, include an "i" after the closing forward slash. Searching with regex offline. To search all of Wikipedia offline using regex, you need to download the Wikipedia database and do the search offline with AutoWikiBrowser's Database ...