#include /** ** User function H: exit, fork, exec, sleep, write ** ** Prints its ID, then spawns 'n' children; exits before they terminate. ** ** Invoked as: userH x n ** where x is the ID character ** n is the number of children to spawn */ USERMAIN(main) { int32_t ret = 0; // return value int count = 5; // child count char ch = 'h'; // default character to print char buf[128]; int whom; // process the argument(s) switch (argc) { case 3: count = str2int(argv[2], 10); // FALL THROUGH case 2: ch = argv[1][0]; break; default: sprint(buf, "userH: argc %d, args: ", argc); cwrites(buf); for (int i = 0; i <= argc; ++i) { sprint(buf, " %s", argv[argc] ? argv[argc] : "(null)"); cwrites(buf); } cwrites("\n"); } // announce our presence swritech(ch); // we spawn user Z and then exit before it can terminate // userZ 'Z' 10 char *argsz[] = { "userZ", "Z", "10", NULL }; for (int i = 0; i < count; ++i) { // spawn a child whom = spawn(ProgZ, argsz); // our exit status is the number of failed spawn() calls if (whom < 0) { sprint(buf, "!! %c spawn() failed, returned %d\n", ch, whom); cwrites(buf); ret += 1; } } // yield the CPU so that our child(ren) can run sleep(0); // announce our departure swritech(ch); exit(ret); return (42); // shut the compiler up! }