Regular Expressions Cookbook, 2nd Edition

Strings with Escapes

Problem

You need a regex that matches a string, which is a sequence of zero or more characters enclosed by double quotes. A string with nothing between the quotes is an empty string. A double quote can be included in the string by escaping it with a backslash, and backslashes can also be used to escape other characters in the string. Strings cannot include line breaks, and line breaks cannot be escaped with backslashes.

Solution

"[^"\\\r\n]*(?:\\.[^"\\\r\n]*)"

Regex options: None

Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

Discussion

This regular expression has the same structure as the one in the preceding recipe. The difference is that we now have two characters with a special meaning: the double quote and the backslash. We exclude both from the characters matched by the two negated character classes. We use ‹\\.› to separately match any escaped character. ‹\\› matches a single backslash, and ‹.› matches any character that is not a line break. Make sure the option “dot matches line breaks” is turned off.

Variations

Strings delimited with single quotes can be matched just as easily:

'[^'\\\r\n]*(?:\\.[^'\\\r\n]*)'

Regex options: None

Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

If your language supports both single-quoted and double-quoted strings, you’ll need to handle those as separate alternatives:

"[^"\\\r\n]*(?:\\.[^"\\\r\n]*)"|'[^'\\\r\n]*(?:\\.[^'\\\r\n]*)'

Regex options: None

Regex flavors: .NET, Java, JavaScript, PCRE, Perl, ...