Character | Meaning | Examples |
_
-
[ ]
If it is at the beginning or the end of a |
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regular expression, it equals ^ or $. | "a_b" matches "a b" or "a(b"; "_ab" only matches |
In other cases, it equals comma, | a line starting with "ab"; "ab_" only matches a line |
space, round bracket, or curly | ending with "ab". |
bracket. |
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It connects two values (the smaller |
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one before it and the bigger one | |
after it) to indicate a range together | (inclusive). |
with [ ]. |
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[16A] matches a string containing any character among 1, 6, and A;
containing any character among 1, 2, 3, 6, and A
Matches a single character (- is a hyphen). contained within the brackets.
To match the character "]", put it at the beginning of
astring within brackets, for example [ ]string]. There is no such limit on "[".
| A character group. It is usually used | (123A) means a character group "123A"; | |
( ) | "408(12)+" matches 40812 or 408121212. But it | ||
with "+" or "*". | |||
| does not match 408. | ||
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| Repeats the character string |
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| specified by the index. A character | (string)\1 repeats string, and a matching string must | |
| string refers to the string within () | ||
| before \. index refers to the | contain stringstring. (string1)(string2)\2 repeats | |
| sequence number (starting from 1 | string2, and a matching string must contain | |
\index | from left to right) of the character | string1string2string2. (string1)(string2)\1\2 | |
| group before \. If only one character | repeats string1 and string2 respectively, and a | |
| group appears before \, index can | matching string must contain | |
| only be 1; if n character groups | string1string2string1string2. | |
| appear before index, index can be |
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| any integer from 1 to n. |
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| [^16A] means to match a string containing any | |
| Matches a single character not | character except 1, 6 or A, and the matching string | |
[^] | can also contain 1, 6 or A, but cannot contain these | ||
contained within the brackets. | |||
| three characters only. For example, [^16A] | ||
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| matches "abc" and "m16", but not 1, 16, or 16A. | |
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\<string | Matches a character string starting | "\<do" matches word "domain" and string "doa". | |
with string. | |||
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string\> | Matches a character string ending | "do\>" matches word "undo" and string "abcdo". | |
with string. | |||
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| Matches character1character2. | "\ba" matches | |
| character1 can be any character | ||
\bcharacter2 | "a" being character2, but it does not match "2a" or | ||
except number, letter or underline, | |||
| "ba". | ||
| and \b equals | ||
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| Matches a string containing | "\Bt" matches "t" in "install", but not "t" in "big | |
\Bcharacter | character, and no space is allowed | ||
top". | |||
| before character. | ||
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