RegExp match lines NOT starting with at-symbol

Question

If I write this regexp (?<=^[\t ]*@).+ I can match only the lines starting with optional spaces (but not newlines) and at-symbol, without matching the at-symbol.

Example: @test Matches "test", but not the " @".

I'm trying to match lines that it first not space character is not the at-symbol. For that purpose I negate the look-behind, resulting in this: (?<!^[\t ]*@).+.

But it matches lines even if their first non-space character is the at-symbol.

I've tried regexps like these: ^[\t ]*[^@].*, (?<=^[\t ]*[^@]).+, (?<=^[\t ]*)(.(?!@)).*. All of then matches lines even their first non-space character is the at-symbol.

How can I do to match lines not starting with optional spaces (not newlines) and the at-symbol?

matches
    matches
m@tches
    m@tches
@Doesn't match
    @Doesn't match

Thanks!

Which language does accept varying length lookbehind (I know none) ? — Tensibai, Feb 10 '16 at 11:03
Split (read line per line), trim, and check the first character with some `startswith` method. No need using a regex. — Wiktor Stribiżew, Feb 10 '16 at 11:05

score 1 · Accepted Answer · answered Feb 10 '16 at 11:11

Your pattern was good except two things:

you need a lookahead (followed with), not a lookbehind
you need to anchor your pattern at the start of the line

So, if you read the text line by line:

^(?![ \t]*@).+

If you read the whole text you need to use the multiline modifier to make ^ to match the start of the line (and not the start of the string by default):

(?m)^(?![ \t]*@).+

(or an other way to switch on this m modifier)

RegExp match lines NOT starting with at-symbol

1 Answers1