Andrew McDonough

Please note: This page is imported from my wiki, which hasn't been updated in over 10 years. Some of the formatting was lost during the import. I'll try to get around to fixing it someday.

======Regular Expressions======

Matching multiple occurences of characters

^ Regexp ^ Meaning ^ | %%/abc/%% | Matches an a followed by zero or more b’s, followed by c. Expressions are greedy—it will match as many as possible. Same as /ab{0,}c/. | | %%/ab+c/%% | Matches an a followed by one or more b’s followed by c. Same as /ab{1,}c/.| | %%/ab?c/%% | Matches an a followed by an optional b followed by c Same as /ab{0,1}c/. This has a different meaning in Perl 5. In Perl 5, the expression: /ab?c/matches an a followed by as few b’s as possible (non-greedy). | | %%/ab{3,5}c/%% | Matches an a followed by between three and five occurrences of b, followed by a c

Matching the beginning and end of a line or string

When placed a the beginning of a regexp, the //caret// (^) will only match the pattern if it occurs starting at the beginning of the line or string. When placed a the end of a regexp, the //dollar/ ($) will only match the pattern if it occurs finishing at the end of the line or string.

e.g. %%s/\.$/./g%% would look for lines that don’t end in a full stop, and place one there.

Character Classes

Sets of characters can be matched by containing the valid set inside square brackets. e.g. %%[aeiou]%% would match all vowels.

The set can be negated by prefixing with a caret e.g. %%<>%% matches all characters except the greater than and less than sign.

Shorthand Character Classes

^ Short version ^ Long version ^ Meaning ^ | \d | %%[0-9]%% | Matches a digit | | \D | %%0-9%% | Matches a non digit | | \w | %%[A-Za-z]%% | Matches a letter | | \W | %%a-za-z%%| Matches a non letter | | \s | %%[ \t\n\r]%%| Matches a whitespace character | | \S | %%0-9%% | Matches a non whitespace character |

Shorthand characters can be used i

Useful Regular expressions for Vim

Change pipe (|) delimited data, as copied from a MySQL console into tab delimited data so it may be pasted into Excel: :%s/[ ]|[ ]/\t/g

Andrew McDonough

Andrew McDonough is a consultant CTO and software developer, currently based between Berlin and London.

Follow Andrew on Twitter or Connect on LinkedIn