SETRESUID(2) BSD System Calls Manual SETRESUID(2)
getresgid, getresuid, setresgid, setresuid -- get or set real, effective
and saved user or group ID
getresgid(gid_t *rgid, gid_t *egid, gid_t *sgid);
getresuid(uid_t *ruid, uid_t *euid, uid_t *suid);
setresgid(gid_t rgid, gid_t egid, gid_t sgid);
setresuid(uid_t ruid, uid_t euid, uid_t suid);
The setresuid() function sets the real, effective and saved user IDs of
the current process. The analogous setresgid() sets the real, effective
and saved group IDs.
Privileged processes may set these IDs to arbitrary values. Unprivileged
processes are restricted in that each of the new IDs must match one of
the current IDs.
Passing -1 as an argument causes the corresponding value to remain
The getresgid() and getresuid() calls retrieve the real, effective, and
saved group and user IDs of the current process, respectively.
Upon successful completion, the value 0 is returned; otherwise the
value -1 is returned and the global variable errno is set to indicate the
[EPERM] The calling process was not privileged and tried to
change one or more IDs to a value which was not the
current real ID, the current effective ID nor the cur-
rent saved ID.
[EFAULT] An address passed to getresgid() or getresuid() was
getegid(2), geteuid(2), getgid(2), getuid(2), issetugid(2), setgid(2),
setregid(2), setreuid(2), setuid(2)
These functions are not part of the IEEE Std 1003.1 (``POSIX.1'') speci-
fication. While they are not completely portable, they are the least
ambiguous way to manage user and group IDs.
These functions first appeared in HP-UX.
BSD March 28, 2017 BSD