Man pages matching name stdin in section 3:

stdin.3.en	debian 10 / manpages-dev
stdin.3.es	debian 10 / manpages-es
stdin.3.ja	debian 10 / manpages-ja-dev
stdin.3.pt	debian 10 / manpages-pt-dev
stdin.3.zh_CN	debian 10 / manpages-zh
stdin.3.zh_TW	debian 10 / manpages-zh
stdin.3.en	debian 11 / manpages-dev
stdin.3.es	debian 11 / manpages-es-dev
stdin.3.fr	debian 11 / manpages-fr-dev
stdin.3.ja	debian 11 / manpages-ja-dev
stdin.3.pt	debian 11 / manpages-pt-dev
stdin.3.zh_CN	debian 11 / manpages-zh
stdin.3.zh_TW	debian 11 / manpages-zh
stdin.3.en	debian 12 / manpages-dev
stdin.3.es	debian 12 / manpages-es-dev
stdin.3.fr	debian 12 / manpages-fr-dev
stdin.3.ja	debian 12 / manpages-ja-dev
stdin.3.ru	debian 12 / manpages-ru-dev
stdin.3.zh_CN	debian 12 / manpages-zh
stdin.3.zh_TW	debian 12 / manpages-zh