pidc語言源碼

A. 編寫一段c語言程序，使進程1創建出2 3 4 子進程，子進程3創建孫進程5 ，5在創建出重孫6

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main()
{
int pid1, pid2, pid3, pid4, pid5, pid6;

pid1 = getpid();
printf("PID = %d\n", pid1);

pid2 = fork();
if (pid2 == 0)
{
printf("PID = %d, Parent PID = %d\n", getpid(), getppid());
sleep(30);
exit(0);
}

pid3 = fork();
if (pid3 == 0)
{
printf("PID = %d, Parent PID = %d\n", getpid(), getppid());

pid5 = fork();
if (pid5 == 0)
{
printf("PID = %d, Parent PID = %d\n", getpid(), getppid());

pid6 = fork();
if (pid6 == 0)
{
printf("PID = %d, Parent PID = %d\n", getpid(), getppid());
sleep(30);
exit(0);
}

sleep(30);
exit(0);
}

sleep(30);
exit(0);
}

pid4 = fork();
if (pid4 == 0)
{
printf("PID = %d, Parent PID = %d\n", getpid(), getppid());
sleep(30);
exit(0);
}

sleep(30);
return 0;
}
每一個進程都會在退出前 sleep 30秒，從而保證能夠用 ps 看到，
編譯 gcc testpid.c -o testpid
然後執行，可以看到
PID = 24913
PID = 24914, Parent PID = 24913
PID = 24916, Parent PID = 24913
PID = 24915, Parent PID = 24913
PID = 24917, Parent PID = 24915
PID = 24918, Parent PID = 24917

ps -ef 的結果
24913 24582 0 11:29 pts/19 00:00:00 ./testpid
24914 24913 0 11:29 pts/19 00:00:00 ./testpid
24915 24913 0 11:29 pts/19 00:00:00 ./testpid
24916 24913 0 11:29 pts/19 00:00:00 ./testpid
24917 24915 0 11:29 pts/19 00:00:00 ./testpid
24918 24917 0 11:29 pts/19 00:00:00 ./testpid