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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 \n escape sequence allows for shorter code by specifying the newline in the string literal, and for faster runtime by eliminating the text formatting operation. Also, the compiler can map the escape sequence to a character encoding system other than ASCII and thus make the code more portable.
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 ...
Escape sequences vary in length. The general format for an ANSI-compliant escape sequence is defined by ANSI X3.41 (equivalent to ECMA-35 or ISO/IEC 2022). [12]: 13.1 The escape sequences consist only of bytes in the range 0x20—0x7F (all the non-control ASCII characters), and can be parsed without looking ahead. The behavior when a control ...
Fuzzy Regular Expressions for Java: Java: LGPL GLib/GRegex [Note 3] GLib reference manual: C: LGPL GNU regex Gnulib reference manual: C LGPL GNU libc, GNU programs GRETA Microsoft Research: C++ Proprietary Gregex: Grovf Inc. RTL, HLS Proprietary: FPGA accelerated >100 Gbit/s regex engine for cybersecurity, financial, e-commerce industries ...
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 ]
However, it can make a regular expression much more concise—eliminating a single complement operator can cause a double exponential blow-up of its length. [26] [27] [28] Regular expressions in this sense can express the regular languages, exactly the class of languages accepted by deterministic finite automata. There is, however, a ...
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# @"\\\\".