ch09-reparent.c

linux编程精髓 源代码

/* ch09-reparent.c --- show that getppid() can change values */

#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <unistd.h>

/* main --- do the work */

int main(int argc, char **argv)
{
	pid_t pid, old_ppid, new_ppid;
	pid_t child, parent;

	parent = getpid();		/* before fork() */

	if ((child = fork()) < 0) {
		fprintf(stderr, "%s: fork of child failed: %s\n",
			argv[0], strerror(errno));
		exit(1);
	} else if (child == 0) {
		old_ppid = getppid();
		sleep(2);		/* see Chapter 10 */
		new_ppid = getppid();
	} else {
		sleep(1);
		exit(0);		/* parent exits after fork() */
	}

	/* only the child executes this */
	printf("Original parent: %d\n", parent);
	printf("Child: %d\n", getpid());
	printf("Child's old ppid: %d\n", old_ppid);
	printf("Child's new ppid: %d\n", new_ppid);

	exit(0);
}