getresgid(2) -- Linux man page
NAMEgetresuid, getresgid - get real, effective and saved user or group ID
DESCRIPTIONgetresuid and getresgid (both introduced in Linux 2.1.44) get the real, effective and saved user ID's (resp. group ID's) of the current process.
RETURN VALUEOn success, zero is returned. On error, -1 is returned, and errno is set appropriately.
- One of the arguments specified an address outside the calling program's address space.
CONFORMING TOThis call is Linux-specific. The prototype is given by glibc since version 2.3.2 provided _GNU_SOURCE is defined.
SEE ALSOgetuid(2), setuid(2), setreuid(2), setresuid(2)