#define _GNU_SOURCE #include <unistd.h> #include <stdio.h> #include <errno.h> #include <grp.h> #include <sys/types.h> #include <sys/syscall.h> int setegid(gid_t gid) { int result; if (gid == (gid_t) ~0) { __set_errno (EINVAL); return -1; } #ifdef __NR_setresgid result = setresgid(-1, gid, -1); if (result == -1 && errno == ENOSYS) /* Will also set the saved group ID if egid != gid, * making it impossible to switch back...*/ #endif result = setregid(-1, gid); return result; }