1 #include <stdio.h>
 2 #include <stdlib.h>
 3 #include <errno.h>
 4 #include <unistd.h>
 5
 6 int main()  7 {  8  pid_t pid;  9 //创建一个进程 10 pid = fork(); 11 //创建失败 12 if (pid < 0) 13  { 14 perror("fork error:"); 15 exit(1); 16  } 17 //子进程 18 if (pid == 0) 19  { 20 printf("I am the child process.\n"); 21 //输出进程ID和父进程ID 22 printf("pid: %d\tppid:%d\n",getpid(),getppid()); 23 printf("I will sleep five seconds.\n"); 24 //睡眠5s，保证父进程先退出 25 sleep(5); 26 printf("pid: %d\tppid:%d\n",getpid(),getppid()); 27 printf("child process is exited.\n"); 28  } 29 //父进程 30 else 31  { 32 printf("I am father process.\n"); 33 //父进程睡眠1s，保证子进程输出进程id 34 sleep(1); 35 printf("father process is exited.\n"); 36  } 37 return 0; 38 }

 1 #include <stdio.h>
 2 #include <unistd.h>
 3 #include <errno.h>
 4 #include <stdlib.h>
 5
 6 int main()  7 {  8  pid_t pid;  9 pid = fork(); 10 if (pid < 0) 11  { 12 perror("fork error:"); 13 exit(1); 14  } 15 else if (pid == 0) 16  { 17 printf("I am child process.I am exiting.\n"); 18 exit(0); 19  } 20 printf("I am father process.I will sleep two seconds\n"); 21 //等待子进程先退出 22 sleep(2); 23 //输出进程信息 24 system("ps -o pid,ppid,state,tty,command"); 25 printf("father process is exiting.\n"); 26 return 0; 27 }

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 #include <unistd.h>
 4 #include <errno.h>
 5
 6 int main()  7 {  8  pid_t pid;  9 //循环创建子进程 10 while(1) 11  { 12 pid = fork(); 13 if (pid < 0) 14  { 15 perror("fork error:"); 16 exit(1); 17  } 18 else if (pid == 0) 19  { 20 printf("I am a child process.\nI am exiting.\n"); 21 //子进程退出，成为僵尸进程 22 exit(0); 23  } 24 else 25  { 26 //父进程休眠20s继续创建子进程 27 sleep(20); 28 continue; 29  } 30  } 31 return 0; 32 }

 1 #include <stdio.h>
 2 #include <unistd.h>
 3 #include <errno.h>
 4 #include <stdlib.h>
 5 #include <signal.h>
 6  7 static void sig_child(int signo);  8  9 int main() 10 { 11  pid_t pid; 12 //创建捕捉子进程退出信号 13  signal(SIGCHLD,sig_child); 14 pid = fork(); 15 if (pid < 0) 16  { 17 perror("fork error:"); 18 exit(1); 19  } 20 else if (pid == 0) 21  { 22 printf("I am child process,pid id %d.I am exiting.\n",getpid()); 23 exit(0); 24  } 25 printf("I am father process.I will sleep two seconds\n"); 26 //等待子进程先退出 27 sleep(2); 28 //输出进程信息 29 system("ps -o pid,ppid,state,tty,command"); 30 printf("father process is exiting.\n"); 31 return 0; 32 } 33 34 static void sig_child(int signo) 35 { 36  pid_t pid; 37 int stat; 38 //处理僵尸进程 39 while ((pid = waitpid(-1, &stat, WNOHANG)) >0) 40 printf("child %d terminated.\n", pid); 41 }

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 #include <unistd.h>
 4 #include <errno.h>
 5
 6 int main()  7 {  8  pid_t pid;  9 //创建第一个子进程 10 pid = fork(); 11 if (pid < 0) 12  { 13 perror("fork error:"); 14 exit(1); 15  } 16 //第一个子进程 17 else if (pid == 0) 18  { 19 //子进程再创建子进程 20 printf("I am the first child process.pid:%d\tppid:%d\n",getpid(),getppid()); 21 pid = fork(); 22 if (pid < 0) 23  { 24 perror("fork error:"); 25 exit(1); 26  } 27 //第一个子进程退出 28 else if (pid >0) 29  { 30 printf("first procee is exited.\n"); 31 exit(0); 32  } 33 //第二个子进程 34 //睡眠3s保证第一个子进程退出，这样第二个子进程的父亲就是init进程里 35 sleep(3); 36 printf("I am the second child process.pid: %d\tppid:%d\n",getpid(),getppid()); 37 exit(0); 38  } 39 //父进程处理第一个子进程退出 40 if (waitpid(pid, NULL, 0) != pid) 41  { 42 perror("waitepid error:"); 43 exit(1); 44  } 45 exit(0); 46 return 0; 47 }