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 p1003.1 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.