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Character
Meaning
Matches any single character, such
.
as a single character, a special
character, and a blank.
Matches the preceding character or
*
character group zero or multiple
times.
Matches the preceding character or
+
character group one or multiple
times
Matches the preceding or
|
succeeding character string
If it is at the beginning or the end of
a regular expression, it equals ^ or
_
$. In other cases, it equals comma,
space, round bracket, or curly
bracket.
It connects two values (the smaller
one before it and the bigger one
-
after it) to indicate a range together
with [ ].
Matches a single character
[ ]
contained within the brackets.
A character group. It is usually used
( )
with "+" or "*".
Repeats the character string
specified by the index. A character
string refers to the string within ()
before \. index refers to the
sequence number (starting from 1
\index
from left to right) of the character
group before \. If only one character
group appears before \, index can
only be 1; if n character groups
appear before index, index can be
any integer from 1 to n.
Matches a single character not
[^]
contained within the brackets.
Matches a character string starting
\<string
with string.
Matches a character string ending
string\>
with string.
Remarks
For example, ".s" matches both "as" and "bs".
For example, "zo*" matches "z" and "zoo"; "(zo)*"
matches "zo" and "zozo".
For example, "zo+" matches "zo" and "zoo", but
not "z".
For example, "def|int" only matches a character
string containing "def" or "int".
For example, "a_b" matches "a b" or "a(b"; "_ab"
only matches a line starting with "ab"; "ab_" only
matches a line ending with "ab".
For example, "1-9" means 1 to 9 (inclusive); "a-h"
means a to h (inclusive).
For example, [16A] matches a string containing
any character among 1, 6, and A; [1-36A] matches
a string containing any character among 1, 2, 3, 6,
and A (- is a hyphen).
"]" can be matched as a common character only
when it is put at the beginning of characters within
the brackets, for example [ ]string]. There is no
such limit on "[".
For example, (123A) means a character group
"123A"; "408(12)+" matches 40812 or 408121212.
But it does not match 408.
For example, (string)\1 repeats string, and a
matching string must contain stringstring.
(string1)(string2)\2 repeats string2, and a
matching string must contain
string1string2string2. (string1)(string2)\1\2
repeats string1 and string2 respectively, and a
matching string must contain
string1string2string1string2.
For example, [^16A] means to match a string
containing any character except 1, 6 or A, and the
matching string can also contain 1, 6 or A, but
cannot contain only these three characters. For
example, [^16A] matches "abc" and "m16", but not
1, 16, or 16A.
For example, "\<do" matches word "domain" and
string "doa".
For example, "do\>" matches word "undo" and
string "abcdo".
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