Another example

Escapee.c

#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>

int main() {
     pid_t pid1;
     pid_t pid2;
     int status;

     if (pid1 = fork()) {
             /* parent process A */
             waitpid(pid1, &status, 0);
     } else if (!pid1) {
	     setpgid(0,0);
	     setsid();
             /* child process B */
             if (pid2 = fork()) {
                     exit(0);
             } else if (!pid2) {
                     /* child process C */
                     sleep(100);
             } else {
                     /* error */
             }
     } else {
             /* error */
	     abort();
     }

     return 0;
}