Nginx exclude substring from a string

I am looking for a to exclude a substring from a string with nginx regex :

exclude a substring : toto
I try many example from internet, but I don't find the correct one.

Not matching :

toto.example.instance.fr
titi-toto.example.instance.fr

Matching :

titi.example.instance.fr
titi-titi.example.instance.fr

I try this regex :

^((?!toto).)\.example\.instance\.fr$

but when I add example.instance.fr, it is matching nothing

The ^((?!toto).) part of your regex matches any single character (.) at the start of the string (^), that does not start a toto char sequence. However, toto cannot be matched even without the lookahead, since after the . part, \.example\.instance\.fr$ comes and definitely requires .example.instance.fr to appear right after that single char matched with ..

You can use

^(?![^.]*toto\.)[^.]+\.example\.instance\.fr$

Details

• ^ - start of string
• (?![^.]*toto\.) - no zero or more chars other than . followed with toto. string allowed at the start
• [^.]+ - one or more chars other than .
• \.example\.instance\.fr$ - .example.instance.fr string till end of the string.

See the regex demo.

Note

If toto must be matched as a whole word, you can add a word boundary:

^(?![^.]*\btoto\.)[^.]+\.example\.instance\.fr$
         ^^