SETRESUID(2)              OpenBSD Programmer's Manual             SETRESUID(2)

NAME
     getresgid, getresuid, setresgid, setresuid - get or set real, effective
     and saved user or group ID

SYNOPSIS
     #include <sys/types.h>
     #include <unistd.h>

     int
     getresgid(gid_t *rgid, gid_t *egid, gid_t *sgid);

     int
     getresuid(uid_t *ruid, uid_t *euid, uid_t *suid);

     int
     setresgid(gid_t rgid, gid_t egid, gid_t sgid);

     int
     setresuid(uid_t ruid, uid_t euid, uid_t suid);

DESCRIPTION
     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
     unchanged.

     The getresgid() and getresuid() calls retrieve the real, effective, and
     saved group and user IDs of the current process, respectively.

RETURN VALUES
     Upon success, these functions return 0; otherwise -1 is returned.

ERRORS
     [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 current saved ID.

     [EFAULT]      An address passed to getresgid() or getresuid() was
                   invalid.

SEE ALSO
     getegid(2), geteuid(2), getgid(2), getuid(2), issetugid(2), setgid(2),
     setregid(2), setreuid(2), setuid(2)

STANDARDS
     These functions are not part of the IEEE Std 1003.1 (``POSIX'')
     specification.  While they are not completely portable, they are the
     least ambiguous way to manage user and group IDs.

HISTORY
     These functions first appeared in HP-UX.

OpenBSD 4.9                      May 31, 2007                      OpenBSD 4.9