3Com 4500G Family Configuration Manual page 968

Character
_
-
[ ]
( )
\index
[^]
\<string
string\>
\bcharacter2
Meaning
Underline. 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.
Hyphen. It connects two values
(the smaller one before it and
the bigger one after it) to
indicate a range together with
[ ].
A range of characters, Matches
any character in the specified
range.
A character group. It is usually
used with "+" or "*".
Repeats a specified character
group for once. A character
group refers to the string in ()
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 \, then index can only be
1; if n character groups appear
before index, then index can be
any integer from 1 to n.
Used to match any character
not in a specified range.
Used to match a character
string starting with string.
Used to match a character
string ending with string.
Used to match
character1character2.
character1 can be any
character except number, letter
or underline, and \b equals
[^A-Za-z0-9_].
2-5
Remarks
For example, "a_b" can match "a b" or
"a(b"; "_ab" can only match a line
starting with "ab"; "ab_" can only match a
line ending with "ab".
For example, "1-9" means numbers from
1 to 9 (inclusive); "a-h" means from a to h
(inclusive).
For example, [16A] can match a string
containing any character among 1, 6,
and A; [1-36A] can match a string
containing any character among 1, 2, 3,
6, and A (with - being a hyphen).
"]" can be matched only when it is put at
the beginning of [ ] if it is used as a
common character in [ ], for example
[ ]string]. There is no such limit on "[".
For example, (123A) means a character
group "123A"; "408(12)+" can match
40812 or 408121212. But it cannot
match 408.
For example, (string)\1 means to repeat
string for once, and (string)\1 must
match a string containing stringstring;
(string1)(string2)\2 means to repeat
string2 for once, and (string1)(string2)\2
must match a string containing
string1string2string2;
(string1)(string2)\1\2 means to repeat
string1 for once first, and then repeat
string2 for once, and
(string1)(string2)\1\2 must match a string
containing string1string2string1string2.
For example, [^16A] means to match a
string containing any character except 1,
6 or A, and the string can also contain 1,
6 or A, but cannot contain these three
characters only. For example, [^16A]
can match "abc" and "m16", but not 1,
16, or 16A.
For example, "\<do" can match word
"domain" or string "doa".
For example, "do\>" can match word
"undo" or string "abcdo".
For example, \ba can match -a, with -
represents character1, and a represents
character2; while \ba cannot match "2a"
or "ba".