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A metacharacter is a character that has a special meaning (instead of a literal meaning) to a computer program, such as a shell interpreter or a regular expression engine. In POSIX extended regular expressions,〔 there are 14 metacharacters that must be preceded by a backslash "\" in order to drop their special meaning and be treated literally inside an expression: the open/close square brackets, "(and " )"; the backslash "\"; the caret "^"; the dollar sign "$"; the period or dot "."; the vertical bar or pipe symbol "|"; the question mark "?"; the asterisk " *"; the plus-sign "+"; open/close curly braces, ""; and open/close parenthesis, "(" and ")".〔 If you want to use any of these characters as a literal in a regex, you need to escape them with a backslash. For example to match the arithmetic expression "(1+1) *3=6" with a regex, then the correct regex is "\(1\+1\)\ *3=6". Otherwise, the parenthesis, plus-sign, and asterisk will have a special meaning. ==Examples== *In some Unix shells and Windows PowerShell, the ; (semicolon) character is a statement separator. *In many regular expression engines, the . (dot) character matches any character, not just a dot. *In XML and HTML, the & (ampersand) character introduces an HTML entity. *In many programming languages, strings are delimited using quotes. In some cases, escape characters (and other methods) are used to avoid delimiter collision. Example : "He said : \"Hello\"". 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「metacharacter」の詳細全文を読む スポンサード リンク
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