setgid - set group identity
int setgid(gid_t gid);
setgid() sets the effective group ID of the calling process. If the
caller is the superuser, the real GID and saved set-group-ID are also
Under Linux, setgid() is implemented like the POSIX version with the
_POSIX_SAVED_IDS feature. This allows a set-group-ID program that is
not set-user-ID-root to drop all of its group privileges, do some un-
privileged work, and then reengage the original effective group ID in a
On success, zero is returned. On error, -1 is returned, and errno is
EPERM The calling process is not privileged (does not have the
CAP_SETGID capability), and gid does not match the real group ID
or saved set-group-ID of the calling process.
getgid(2), setegid(2), setregid(2), capabilities(7), credentials(7)
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