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Full stop (dot, period) and \N

 

 

 

Outside a character class, a dot in the pattern matches any one character in the subject string except (by default) a character that signifies the end of a line.

When a line ending is defined as a single character, dot never matches that character; when the two-character sequence CRLF is used, dot does not match CR if it is immediately followed by LF, but otherwise it matches all characters (including isolated CRs and LFs). When any Unicode line endings are being recognized, dot does not match CR or LF or any of the other line ending characters.

 

The behaviour of dot with regard to newlines can be changed. If the PCRE_DOTALL option is set, a dot matches any one character, without exception. If the two-character sequence CRLF is present in the subject string, it takes two dots to match it.

 

The handling of dot is entirely independent of the handling of circumflex and dollar, the only relationship being that they both involve newlines. Dot has no special meaning in a character class.

 

The escape sequence \N behaves like a dot, except that it is not affected by the PCRE_DOTALL option. In other words, it matches any character except one that signifies the end of a line. Perl also uses \N to match characters by name; PCRE does not support this.


 

 

 

Philip Hazel

University Computing Service

Cambridge CB2 3QH, England.

Last updated: 12 November 2013

Copyright © 1997-2013 University of Cambridge.


 

 

 

 

 

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