Cisco Systems Cisco IOS XR manual Special Characters, Character Pattern Ranges

Appendix A Understanding Regular Expressions, Special Characters, and Patterns

Special Characters

Special Characters

Certain keyboard characters have special meaning when used in regular expressions. Table A-1lists the keyboard characters that have special meaning.

Table A-1	Characters with Special Meaning
Character		Special Meaning
.		Matches any single character, including white space.
*		Matches 0 or more sequences of the pattern.
+		Matches 1 or more sequences of the pattern.
?		Matches 0 or 1 occurrences of the pattern.
^		Matches the beginning of the string.
$		Matches the end of the string.
_ (underscore)		Matches a comma (,), left brace ({), right brace (}), left parenthesis ( ( ), right
		parenthesis ( ) ), the beginning of the string, the end of the string, or a space.

To use these special characters as single-character patterns, remove the special meaning by preceding each character with a backslash (\). In the following examples, single-character patterns matching a dollar sign, an underscore, and a plus sign, respectively, are shown.

\$ \_ \+

Character Pattern Ranges

A range of single-character patterns can be used to match command output. To specify a range of single-character patterns, enclose the single-character patterns in square brackets ([ ]). Only one of these characters must exist in the string for pattern-matching to succeed. For example, [aeiou] matches any one of the five vowels of the lowercase alphabet, while [abcdABCD] matches any one of the first four letters of the lowercase or uppercase alphabet.

You can simplify a range of characters by entering only the endpoints of the range separated by a dash (–), as in the following example:

[a–dA–D]

To add a dash as a single-character pattern in the search range, include another dash and precede it with a backslash:

[a–dA–D\–]

A bracket (]) can also be included as a single-character pattern in the range:

[a–dA–D\–\]]

Invert the matching of the range by including a caret (^) at the start of the range. The following example matches any letter except the ones listed:

[^a–dqsv]

The following example matches anything except a right square bracket (]) or the letter d:

[^\]d]

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