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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 ...
In CP/M, 86-DOS, MS-DOS, PC DOS, DR-DOS, and their various derivatives, the SUB character was also used to indicate the end of a character stream, [citation needed] and thereby used to terminate user input in an interactive command line window (and as such, often used to finish console input redirection, e.g. as instigated by the command COPY ...
The second is a link to the article that details that symbol, using its Unicode standard name or common alias. (Holding the mouse pointer on the hyperlink will pop up a summary of the symbol's function.); The third gives symbols listed elsewhere in the table that are similar to it in meaning or appearance, or that may be confused with it;
Generally, an escape character is not a particular case of (device) control characters, nor vice versa.If we define control characters as non-graphic, or as having a special meaning for an output device (e.g. printer or text terminal) then any escape character for this device is a control one.
He later added this capability to the Unix editor ed, which eventually led to the popular search tool grep's use of regular expressions ("grep" is a word derived from the command for regular expression searching in the ed editor: g/re/p meaning "Global search for Regular Expression and Print matching lines"). [15]
A Unicode character is assigned a unique Name (na). [1] The name is composed of uppercase letters A–Z, digits 0–9, hyphen-minus and space.Some sequences are excluded: names beginning with a space or hyphen, names ending with a space or hyphen, repeated spaces or hyphens, and space after hyphen are not allowed.
0x1B (escape, ESC, \e (GCC only), ^[). Introduces an escape sequence. Control characters may be described as doing something when the user inputs them, such as code 3 (End-of-Text character, ETX, ^C) to interrupt the running process, or code 4 (End-of-Transmission character, EOT, ^D), used to end text input on Unix or to exit a Unix shell ...
As of Unicode version 16.0, there are 155,063 characters with code points, covering 168 modern and historical scripts, as well as multiple symbol sets. This article includes the 1,062 characters in the Multilingual European Character Set 2 subset, and some additional related characters.