August 2012
Intermediate to advanced
609 pages
19h 16m
English
Content preview from Regular Expressions Cookbook, 2nd Edition
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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 ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.