redhat man page for setresuid

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

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

SYNOPSIS
       #include <unistd.h>

       int setresuid(uid_t ruid, uid_t euid, uid_t suid);
       int setresgid(gid_t rgid, gid_t egid, gid_t sgid);

DESCRIPTION
       setresuid sets the real user ID, the effective user ID, and the saved set-user-ID of the current process.

       Unprivileged  user  processes  (i.e.,  processes with each of real, effective and saved user ID nonzero) may change the real, effective and
       saved user ID, each to one of: the current uid, the current effective uid or the current saved uid.

       The super-user may set real, effective and saved user ID to arbitrary values.

       If one of the parameters equals -1, the corresponding value is not changed.

       Completely analogously, setresgid sets the real, effective and saved group ID's of the current process, with the same restrictions for pro-
       cesses with each of real, effective and saved user ID nonzero.

RETURN VALUE
       On success, zero is returned.  On error, -1 is returned, and errno is set appropriately.

ERRORS
       EPERM  The current process was not privileged and tried to change the IDs is a not allowed way.

CONFORMING TO
       This call is nonstandard.

HISTORY
       This  system  call  was first introduced in HP-UX.  It is available under Linux since Linux 2.1.44.  These days it is also found in FreeBSD
       (for emulation of Linux binaries).

NOTES
       Under HP-UX and FreeBSD the prototype is found in <unistd.h>.  Under Linux there is so far no include file giving the prototype - this is a
       glibc bug. Programs using this system call must add the prototype themselves.

SEE ALSO
       getuid(2), setuid(2), setreuid(2), getresuid(2)

Linux 2.1.44							    2001-11-15							      SETRESUID(2)