pid3              858 user/usertests.c   int pid1, pid2, pid3;
pid3              880 user/usertests.c   pid3 = fork();
pid3              881 user/usertests.c   if (pid3 < 0) {
pid3              885 user/usertests.c   if (pid3 == 0) {
pid3              903 user/usertests.c   kill(pid3);