A Practical Guide to Red Hat® Linux® 8

Bracketing Expressions

You can use quoted parentheses, \( and \), to bracket a regular expression. The string that the bracketed regular expression matches can be recalled, as explained in “Quoted Digit,” following. A regular expression does not attempt to match quoted parentheses. Thus a regular expression enclosed within quoted parentheses matches what the same regular expression without the parentheses would match. The expression /\(rexp\)/ matches what /rexp/ would match, and /a\(b*\)c/ matches what /ab*c/ would match.

You can nest quoted parentheses. The bracketed expressions are identified only by the opening \( , so there is no ambiguity in identifying them. The expression /\([a–z]\([A–Z]*\)x\)/ consists of two bracketed expressions, one ...