Cisco ASR 9000 Getting Started Manual page 141
Cisco systems router getting started guide
Hide thumbs
Also See for ASR 9000:
- Command reference manual (1138 pages) ,
- Routing configuration manual (702 pages) ,
- Reference manual (696 pages)
Table of Contents
Advertisement
Appendix A
Understanding Regular Expressions, Special Characters, and Patterns
Parentheses Used for Pattern Recall
F I N A L D R A F T — C i s c o C o n f i d e n t i a l
To create a regular expression that recalls a previous pattern, use parentheses to indicate memory of a
specific pattern and a backslash (\) followed by a digit to reuse the remembered pattern. The digit
specifies the occurrence of a parenthesis in the regular expression pattern. When there is more than one
remembered pattern in the regular expression, \1 indicates the first remembered pattern, \2 indicates the
second remembered pattern, and so on.
The following regular expression uses parentheses for recall:
a(.)bc(.)\1\2
This regular expression matches an a followed by any character (call it character number 1), followed by
bc followed by any character (character number 2), followed by character number 1 again, followed by
character number 2 again. So, the regular expression can match aZbcTZT. The software remembers that
character number 1 is Z and character number 2 is T, and then uses Z and T again later in the regular
expression.
Cisco ASR 9000 Series Aggregation Services Router Getting Started Guide
A-5
OL-17502-01
Advertisement
Table of Contents
