\d
- any number
\D
- any non-digital character
\w
- any letter
[abc123]
- any character specified in square brackets
[abc123]?
- any character specified in square brackets or the absence of a character
[abc123]+
- a sequence of any characters specified in square brackets
[abc123]*
- the sequence of any characters specified in square brackets or the absence of a character
.
- any character
.+
- an arbitrary sequence of any characters
.*
- an arbitrary sequence of any characters or the absence of a character
b+
- arbitrary character sequence "b"
b*
- an arbitrary sequence of the "b" character or its absence
\.
- The dot symbol "."
.?
- any symbol or its absence
b?
- the "b" symbol or its absence
abc|xyz
- one of the words (abc or xyz)
(abc)
- the expression in parentheses is remembered for subsequent replacement (see the replacement options below)
^
- beginning of the line
$
- end of line