Is there an API call, to which you pass a user name and password and says if they are correct by looking at the Linux's user/password database (/etc/passwd or shadowed passwords)?. I would like it to be portable to Unix and *BSD if possible.
If there is a way to get all the OS's user and password database that would do the job too.
I first asked here: http://www.experts-exchange.com/Programming/Programming_Languages/Cplusplus/Q_21095702.html
But as this question is somewhat different and specific to Linux/*nix/*BSD platform, I'm posting it here.