Regular Expressions Cookbook

2.19. Insert Literal Text into the Replacement Text

Problem

Search and replace any regular expression match literally with the eight characters $%\*$1\1.

Solution

$%\*$$1\1

Replacement text flavors: .NET, JavaScript

\$%\\*\$1\\1

Replacement text flavor: Java

$%\*\$1\\1

Replacement text flavor: PHP

\$%\*\$1\\1

Replacement text flavor: Perl

$%\*$1\\1

Replacement text flavors: Python, Ruby

Discussion

When and how to escape characters in replacement text

This recipe shows you the different escape rules used by the various replacement text flavors. The only two characters you may ever need to escape in the replacement text are the dollar sign and the backslash. The escape characters are also the dollar sign and the backslash.

The percentage sign and asterisk in this example are always literal characters, though a preceding backslash may be treated as an escape instead of a literal backslash. «$1» and/or «\1» are a backreference to a capturing group. Recipe 2.21 tells you which flavors use which syntax for backreferences.

The fact that this problem has five different solutions for seven replacement text flavors demonstrates that there really is no standard for replacement text syntax.

.NET and JavaScript

.NET and JavaScript always treat a backslash as a literal character. Do not escape it with another backslash, or you’ll end up with two backslashes in the replacement.

A lone dollar sign is a literal character. Dollar signs need to be escaped only when they are followed by a digit, ampersand, backtick, straight ...