/*
 * Sample program for setgid system call  - No.46
 *
 * setgid - set group identity
 *
 * Synopsis
 *     #include <sys/types.h>
 *     #include <unistd.h>
 *
 *     int setgid(gid_t gid);
 *
 * Description
 *     setgid sets the effective groupe ID of the current process.
 *     If the caller is the superuser, the real and saved group
 *     ID's are also set
 *
 *     Under Linux, setgid is implemented like the POSIX version
 *     with the _POSIX_SAVED_IDS feature. This allows a setgid
 *     (other than root) program to drop all of its group privileges,
 *     do some un-privileged work, and then re-engage the original
 *     effective group ID in a secure manner.
 *
 *     If the user is root or the program si setgid root, special
 *     care must be taken. The setgid function checks the effective
 *     gid of the caller and if it is the superuser, all process
 *     related group ID's are set to gid. After this has occured,
 *     it is impossible for the program to regain root privileges.
 *
 *     Thus, a setgid-root program wishing to temporarily drop
 *     root privileges, assume the identity of a non-root group,
 *     and then regain root privileges afterwards cannot use
 *     setgid. You can accomplish this with the (non-POSIX, BSD)
 *     call setegid.
 */

#include <stdio.h>

main()
{
	setgid(7);
	printf("gid = %d\n", getgid());
}