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For example, the set of characters matched by \w (word characters) is expanded to include letters and accented letters as defined by Unicode properties. Such matching is slower than the normal (ASCII-only) non-UCP alternative. Note that the UCP option requires the library to have been built to include Unicode support (this is the default for ...
The matching algorithms of the library are based on the PCRE library, but not all of the PCRE library is interfaced and some parts of the library go beyond what PCRE offers. Currently PCRE version 8.40 (release date 2017-01-11) is used. Erlang: erlang.org: Apache 2.0: Standard library includes PCRE-based re module. The matching algorithms of ...
An escape character may not have its own meaning, so all escape sequences are of two or more characters. Escape characters are part of the syntax for many programming languages, data formats, and communication protocols. For a given alphabet an escape character's purpose is to start character sequences (so named escape sequences), which have to ...
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 ...
Like old typewriters, plain base characters (white spaces, punctuation characters, symbols, digits, or letters) can be followed by one or more non-spacing symbols (usually diacritics, like accent marks modifying letters) to form a single printable character; but Unicode also provides a limited set of precomposed characters, i.e. characters that ...
In computer science, an illegal character is a character that is not allowed by a certain programming language, protocol, or program. [1] To avoid illegal characters, some languages may use an escape character which is a backslash followed by another character.
When an escape character is inside a string literal, it means "this is the start of the escape sequence". Every escape sequence specifies one character which is to be placed directly into the string. The actual number of characters required in an escape sequence varies. The escape character is on the top/left of the keyboard, but the editor ...
Encoding input or escaping dangerous characters. For instance, in PHP, using the htmlspecialchars() function to escape special characters for safe output of text in HTML and the mysqli::real_escape_string() function to isolate data which will be included in an SQL request can protect against SQL injection.