Working with the Unix OS

Processes II
9. PROCESSES (II)
FORK
! /* fork.c */
#include
main()
{
int pid;
printf("original process with PID %d and PPID %d\n", getpid(), getppid());
pid = fork(); /* duplicate process */
}
if (pid != 0) {/* parent */
printf("parent process with PID %d and PPID %d\n",
getpid(), getppid());
printf("child's PID is %d\n", pid);
}
else{ /* child */
printf("child process with PID %d and PPID %d\n",
getpid(), getppid());
}
printf("PID %d terminates\n", getpid());
original process with PID 134 and PPID 120
parent process with PID 134 and PPID 120
child's PID is 135
child process with PID 135 and PPID 134
PID 135 terminates
PID 134 terminates
! /* orphan.c */
#include
main()
{
int pid;
printf("original process with PID %d and PPID %d\n", getpid(), getppid());
}
pid = fork(); /* duplicate process */
if (pid != 0){ /* parent */
printf("parent process with PID %d and PPID %d\n",
getpid(), getppid());
printf("child's PID is %d\n", pid);
}
else { /* child */
sleep(5); /* terminate parent first */
printf("child process with PID %d and PPID %d\n",
getpid(), getppid());
}
printf("PID %d terminates\n", getpid());
original process with PID 154 and PPID 140
parent process with PID 154 and PPID 140
child's PID is 155
PID 154 terminates
parent dies
child process with PID 155 and PPID 1 init adopts child
PID 155 terminates
122