setuid - set user ID

Syntax	#include <unistd.h> Optional #include <sys/types.h> int setuid(uid_t uid);
Description	If the process has appropriate privileges, the setuid() function sets the real user ID, effective user ID, and the saved set-user-ID to uid. If the process does not have appropriate privileges, but uid is equal to the real user ID or the saved set-user-ID, setuid() sets the effective user ID to uid. The real user ID and saved set-user-ID remain unchanged.
Return val.	0 –1	if successful. if unsuccessful. errno is set to indicate the error.
Errors	setuid() will fail if:
	EPERM	The process does not have appropriate privileges and uid does not match the real user ID or the saved set-user-ID.
Notes	setuid() is frequently used to relinquish privileges that are no longer needed in programs that have the s-bit for the owner set (especially root). Such programs often need the privileges granted by the s-bit only for very specific tasks. When the privileges are no longer required, they can be relinquished by a call in the form given below: erg = setuid(getuid());
See also	setpgid(), sys/types.h, unistd.h.