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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 ...
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 //.
A regular expression ... i.e. preceded by an escape sequence, in this case, the backslash \. ... only a few regex engines (e.g., Perl's and Java's) ...
The backslash (\) escape character typically provides two ways to include double-quotes inside a string literal, either by modifying the meaning of the double-quote character embedded in the string (\" becomes "), or by modifying the meaning of a sequence of characters including the hexadecimal value of a double-quote character (\x22 becomes ").
Preceding any other character with a backslash is harmless. For example, insource:/yes\.\no/ will search for pages containing the literal string "yes.no" (case-sensitive). Regex experts should note that \n does not mean "newline," \d does not mean "digit," and so on: In MediaWiki syntax, the only use of \ is to escape metacharacters.
Extreme examples occur when these are combined – Uniform Naming Convention paths begin with \\, and thus an escaped regular expression matching a UNC name begins with 8 backslashes, "\\\\\", due to needing to escape the string and the regular expression. Using raw strings reduces this to 4 (escaping in the regular expression), as in C# @"\\\\".
In C and many derivative programming languages, a string escape sequence is a series of two or more characters, starting with a backslash \. [3]Note that in C a backslash immediately followed by a newline does not constitute an escape sequence, but splices physical source lines into logical ones in the second translation phase, whereas string escape sequences are converted in the fifth ...
Java Apache java.util.regex Java's User manual: Java GNU GPLv2 with Classpath exception jEdit: JRegex JRegex: Java BSD MATLAB: Regular Expressions: MATLAB Language: Proprietary Oniguruma: Kosako: C BSD Atom, Take Command Console, Tera Term, TextMate, Sublime Text, SubEthaEdit, EmEditor, jq, Ruby: Pattwo Stevesoft Java (compatible with Java 1.0 ...