SETREGID(2) BSD Programmer's Manual SETREGID(2)
setregid - set real and effective group ID
setregid(gid_t rgid, gid_t egid);
The real and effective group ID's of the current process are set to the
arguments. Unprivileged users may change the real group ID to the effec-
tive group ID and vice-versa; only the super-user may make other changes.
Supplying a value of -1 for either the real or effective group ID forces
the system to substitute the current ID in place of the -1 parameter.
The setregid() function was intended to allow swapping the real and ef-
fective group IDs in set-group-ID programs to temporarily relinquish the
set-group-ID value. This function did not work correctly, and its pur-
pose is now better served by the use of the setegid() function (see
When setting the real and effective group IDs to the same value, the
standard setgid() function is preferred.
Upon successful completion, a value of 0 is returned. Otherwise, a value
of -1 is returned and errno is set to indicate the error.
[EPERM] The current process is not the super-user and a change other
than changing the effective group-id to the real group-id was
getgid(2), setegid(2), setgid(2), setuid(2)
The setregid function call appeared in 4.2BSD and was dropped in 4.4BSD.
4.2 Berkeley Distribution April 16, 1994 1