getlogin - get login name
Getlogin returns a pointer to the login name as found in /etc/utmp. It
may be used in conjunction with getpwnam to locate the correct password
file entry when the same user ID is shared by several login names.
If getlogin is called within a process that is not attached to a
terminal, or if there is no entry in /etc/utmp for the process's
terminal, getlogin returns a null pointer. A reasonable procedure for
determining the login name is to first call getlogin and if it fails, to
getpwent(3), utmp(5), ttyslot(3)
Returns a null pointer if the name cannot be found.
The return values point to static data whose content is overwritten by