Example: Process Creation in Unix

int pid;

int status = 0;

if (pid = fork()) {

/* parent */

…..

pid = wait(&status);

} else {

/* child */

…..

exit(status);

}

Parent uses wait to sleep until the child exits; wait returns child pid and status.

Wait variants allow wait on a specific child, or notification of stops and other signals.

The fork syscall returns twice: it returns a zero to the child and the child process ID (pid) to the parent.