Man pages matching name strspn in section 3:

strspn.3.en	debian 10 / manpages-dev
strspn.3.es	debian 10 / manpages-es
strspn.3.ja	debian 10 / manpages-ja-dev
strspn.3.pl	debian 10 / manpages-pl-dev
strspn.3.pt	debian 10 / manpages-pt-dev
strspn.3.en	debian 11 / manpages-dev
strspn.3.es	debian 11 / manpages-es-dev
strspn.3.fr	debian 11 / manpages-fr-dev
strspn.3.ja	debian 11 / manpages-ja-dev
strspn.3.pl	debian 11 / manpages-pl-dev
strspn.3.pt	debian 11 / manpages-pt-dev
strspn.3.de	debian 12 / manpages-de-dev
strspn.3.en	debian 12 / manpages-dev
strspn.3.es	debian 12 / manpages-es-dev
strspn.3.fr	debian 12 / manpages-fr-dev
strspn.3.ja	debian 12 / manpages-ja-dev
strspn.3.pl	debian 12 / manpages-pl-dev
strspn.3.ru	debian 12 / manpages-ru-dev