kern/user/progH.c

#include <common.h>

/**
** 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!
}