\ |
Marks the next character as either a special
character or a literal. For example, n matches the
character n, whereas \n matches a newline
character. The sequence \\ matches \ and \( matches
(. |
^ |
Matches the beginning of input. |
$ |
Matches the end of input. |
* |
Matches the preceding character zero or more
times. For example, zo* matches either z or zoo. |
+ |
Matches the preceding character one or more
times. For example, zo+ matches zoo but not z. |
? |
Matches the preceding character zero or one
time. For example, a?ve? matches the ve in never. |
. |
Matches any single character except a newline
character. |
(pattern) |
Matches a pattern and remembers the match. The
matched substring can be retrieved from the resulting matches collection
by using this code: Item [0]...[n]. To match parentheses
characters ( ), use \( or \). |
x|y |
Matches either x or y.
For example, z|wood matches z or wood. (z|w)oo matches zoo or wood. |
{n} |
n is a non-negative integer.
Matches exactly n times. For example, o{2} does
not match the o in Bob, but matches the first two os
in foooood. |
{n,} |
In this expression, n is
a non-negative integer. Matches the preceding character at least n times.
For example, o{2,} does not match the o in Bob and
matches all the os in foooood. The o{1,} expression
is equivalent to o+ and o{0,} is
equivalent to o*. |
{n,m} |
The m and n variables
are non-negative integers. Matches the preceding character at least n and
at most m times. For example, o{1,3} matches
the first three os in fooooood. The o{0,1} expression
is equivalent to o?. |
[xyz] |
A character set. Matches any one of the enclosed
characters. For example, [abc] matches the a in plain. |
[^xyz] |
A negative character set. Matches any character
that is not enclosed. For example, [^abc] matches
the p in plain. |
[a-z] |
A range of characters. Matches any character
in the specified range. For example, [a-z] matches
any lowercase alphabetic character in the English alphabet. |
[^m-z] |
A negative range of characters. Matches any
character that is not in the specified range. For example, [m-z] matches
any character that is not in the range m through z. |
\A |
Matches only at beginning of a string. |
\b |
Matches a word boundary, that is, the position
between a word and a space. For example, er\b matches
the er in never but not the er in verb. |
\B |
Matches a nonword boundary. The ea*r\B expression
matches the ear in never early. |
\d |
Matches a digit character. |
\D |
Matches a non-digit character. |
\f |
Matches a form-feed character. |
\n |
Matches a newline character. |
\r |
Matches a carriage return character. |
\s |
Matches any white space including spaces, tabs,
form-feed characters, and so on. |
\S |
Matches any non-white space character. |
\t |
Matches a tab character. |
\v |
Matches a vertical tab character. |
\w |
Matches any word character including underscore.
This expression is equivalent to [A-Za-z0-9_]. |
\W |
Matches any non-word character. This expression
is equivalent to [^A-Za-z0-9_]. |
\z |
Matches only the end of a string. |
\Z |
Matches only the end of a string, or before
a newline character at the end. |