128
Character Meaning
Remarks
|
Matches the preceding or
succeeding character string
For example, “def|int” only matches a character
string containing “def” or “int”.
_
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.
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”.
-
It connects two values (the smaller
one before it and the bigger one
after it) to indicate a range together
with [ ].
For example, “1-9” means 1 to 9 (inclusive); “a-h”
means a to h (inclusive).
[ ]
Matches a single character
contained within the brackets.
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 “[”.
( )
A character group. It is usually used
with “+” or “*”.
For example, (123A) means a character group
“123A”; “408(12)+” matches 40812 or
408121212. But it does not match 408.
\index
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
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.
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.
[^]
Matches a single character not
contained within the brackets.
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 these three characters only. For
example, [^16A] matches “abc” and “m16”, but
not 1, 16, or 16A.
\<string
Matches a character string starting
with
string
.
For example, “\<do” matches word “domain” and
string “doa”.
string\>
Matches a character string ending
with
string
.
For example, “do\>” matches word “undo” and
string “abcdo”.
\bcharacter2
Matches
character1character2.
character1
can be any character
except number, letter or underline,
and \b equals [^A-Za-z0-9_].
For example, “\ba” matches “-a” with “-“ being
character1,
and “a” being
character2,
but it does
not match “2a” or “ba”
.
