Metacharacters Defined |
Metacharacter Examples |
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MChar |
Definition |
Pattern |
Sample Matches |
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^ |
匹配字串開頭 |
^abc |
abc, abcdefg, abc123, … |
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$ |
匹配字串結尾 |
abc$ |
abc, endsinabc, 123abc, … |
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. |
任何字元(特殊字元除外) |
a.c |
abc, aac, acc, adc, aec, … |
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| |
擇一匹配 |
text|ted |
ted, text |
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{…} |
量詞Explicit quantifier notation. |
ab{2}c |
abbc |
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[…] |
括號內任一字元 |
a[bB]c |
abc, aBc |
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(…) |
Logical grouping of part of an expression. |
(abc){2} |
abcabc |
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* |
0個或是N個先前的字元 |
ab*c |
ac, abc, abbc, abbbc, … |
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+ |
1個或是N個先前的字元 |
ab+c |
abc, abbc, abbbc, … |
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? |
0個或是1個先前的字元 |
ab?c |
ac, abc |
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\ |
跳脫字元或顯示符號本身 |
a\sc |
a c |
Escaped Char | Description |
ordinary characters | Characters other than . $ ^ { [ ( | ) ] } * + ? \ match themselves.(顯示特殊符號) |
\a | Matches a bell (alarm) \u0007. |
\b | Matches a backspace \u0008 if in a []; otherwise matches a word boundary (between \w and \W characters). 比對英文字的邊界，例如空格 |
\t | Matches a tab \u0009. |
\r | Matches a carriage return \u000D. |
\v | Matches a vertical tab \u000B. |
\f | Matches a form feed \u000C. 文字中有發生 “換頁” 的行為 則可以比對成功 |
\n | Matches a new line \u000A. 換行符號 |
\e | Matches an escape \u001B. |
\o40 | 比對八進位，其中40是八進位數目 |
\x20 | 比對十六進位，其中20是十六進位數目 |
\cC | Matches an ASCII control character; for example \cC is control-C. |
\u0020 | Matches a Unicode character using a hexadecimal representation (exactly four digits). |
\* | When followed by a character that is not recognized as an escaped character, matches that character. For example, \* is the same as \x2A. |
/t | Tab字元 |
Char Class | Description |
[aeiou] | 括號內任一字元 |
[^aeiou] | 括號內字元之外的字元 |
[0-9a-fA-F] | 用 –表示連續的數字或字母 |
\p{name} | Matches any character in the named character class specified by {name}. Supported names are Unicode groups and block ranges. For example, Ll, Nd, Z, IsGreek, IsBoxDrawing. |
\P{name} | Matches text not included in groups and block ranges specified in {name}. |
\w | 等同[a-zA-Z0-9_]，任何字母、數字和底線 |
\W | 等同[^a-zA-Z0-9_]，ASCII任何字元之外 |
\s | 任一個空白字元（White space character），\s is equivalent to [ \f\n\r\t\v]. |
\S | 任一個非空白字元，\S is equivalent to [^ \f\n\r\t\v]. |
\d | 等同[0-9]，任何數字 |
\D | 等同[^0-9]，任何數字之外的字元 |
(?=p) | 要求後面的字元必須匹配p(回傳時不包含p字元) |
(?!p) | 要求後面的字元不匹配p |