sorry i should have specified...

I'm editing the debian pmount utility to work with gentoo, hal, and gvm, instead of using fstab-sync which is unsafe and just didn't work period for me, and want to allow users in the plugdev group to unmount devices. So far I can get the gid of the mounting user through /etc/mtab, and can get a vector of user names in that group through getgrgid(). I would like to check to see if the calling user (getuid()) is in the group that mounted the volume to allow that user to unmount it.

is there a way to use either method in c, or preferrebly a function that i can call to get either an id or a user name?

upon further googling, getpwnam() looks promising, i'll get back to you if it works

Thanks!