Getting Started Guide

131
Character Meanin
g
Exam
p
les
_
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.
"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 [ ].
"1-9" means 1 to 9 (inclusive); "a-h" means a to h
(inclusive).
[ ]
Matches a single character
contained within the brackets.
[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).
To match the character "]", put it at the beginning of
a string within brackets, for example [ ]string]. There
is no such limit on "[".
( )
A character group. It is usually used
with "+" or "*".
(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.
(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.
[^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.
"\<do" matches word "domain" and string "doa".
string\>
Matches a character string ending
with string.
"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_].
"\ba" matches "-a" with "-" being character1, and
"a" being character2, but it does not match "2a" or
"ba".
\Bcharacter
Matches a string containing
character, and no space is allowed
before character.
"\Bt" matches "t" in "install", but not "t" in "big
top".