Editing Metacharacter (section)

{{short description|Character that has a special meaning to a computer program}}
{{Lead rewrite|reason=definition and lead are only about regular expression metacharacters, but article is not |date=April 2019}}
A '''metacharacter''' is a [[Character (computing)|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 (<code>\</code>) — in order to drop their special meaning and be treated literally inside an expression: opening and closing square brackets (<code>[</code> and <code>]</code>); backslash (<code>\</code>); caret (<code>^</code>); dollar sign (<code>$</code>); period/full stop/dot (<code>.</code>); vertical bar/pipe symbol (<code>|</code>); question mark (<code>?</code>); asterisk (<code>*</code>); plus and minus signs (<code>+</code> and <code>-</code>); opening and closing curly brackets/braces (<code>{</code> and <code>}</code>); and opening and closing parentheses (<code>(</code> and <code>)</code>).

For example, to match the arithmetic expression <code>(1+1)*3=6</code> with a regex, the correct regex is <code>\(1\+1\)\*3=6</code>; otherwise, the parentheses, plus sign, and asterisk will have special meanings.