osx man page for setruid

SETRUID(3)						   BSD Library Functions Manual 						SETRUID(3)

NAME
     setruid, setrgid -- set user and group ID

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <unistd.h>

     int
     setruid(uid_t ruid);

     int
     setrgid(gid_t rgid);

DESCRIPTION
     The setruid() function (setrgid()) sets the real user ID (group ID) of the current process.

RETURN VALUES
     Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the
     error.

COMPATIBILITY
     The use of these calls is not portable.  Their use is discouraged; they will be removed in the future.

ERRORS
     The functions fail if:

     [EPERM]		The user is not the super user and the ID specified is not the real or effective ID.

SEE ALSO
     getgid(2), getuid(2), setegid(2), seteuid(2), setgid(2), setuid(2)

HISTORY
     The setruid() and setrgid() syscalls appeared in 4.2BSD and were dropped in 4.4BSD.

BSD
								   June 2, 1993 							       BSD