进程 (二).exec（1）

#include <stdio.h>
#include <unistd.h> //sleep函数在这里面声明

int main()
{
  int i=0;
  for(i=0;i<5;i++)
  {
    sleep(2);
    printf("%d loop...(there are %d times left)\n",i+1,5-i-1);
  }
  return 0;
}

emacs@ubuntu:~/c$ alias  gtc
alias gtc='gcc -Wall -g -o'
emacs@ubuntu:~/c$ gtc z.x z.c
emacs@ubuntu:~/c$ ./z.x
1 loop...(there are 4 times left)
2 loop...(there are 3 times left)
3 loop...(there are 2 times left)
4 loop...(there are 1 times left)
5 loop...(there are 0 times left)
emacs@ubuntu:~/c$

#include <stdio.h>
#include <unistd.h>
#include <sys/wait.h>
#include <stdlib.h> //exit 函数在里面声明

int main()
{
  pid_t fret=0; //创建一个变量用来存放fork返回值

  fret=fork(); 
  if(0 < fret) //如果pe的值大于0,就代表为父进程，fret的值就是子进程的进程号
  {
    int pid=0,status=0;
    
    sleep(3);
    printf("this is the parent process(%d),wait for child(%d)...\n",getpid(),fret); 
    pid = wait(&status); //使用阻塞模式等待子进程退出
    if(-1 !=  pid ) printf("this is the father process, my pid is %d, child process is %d, the wait return value is %d \n",getpid(),fret,WEXITSTATUS(status)); //再次显示父子进程PID，和子进程退出的状态
    else printf("wait error\n");
  }
  else if(0 == fret) //fork返回值为0的时候代表子进程
  {
    char *s="/home/emacs/c/z.x";  //定义一个字符指针存放可执行程序的路径
    char *c="z.x"; //定义一个字符指针存放可执行文件名
    printf ("this is child, pid is :%d, my father pid is %d\n",getpid(),getppid()); //显示父子进程PID信息
    execl(s,c,(char *)0); //进行进程替换， use NULL instead of (char *)0
  } 
  else 
  {
    printf("fork error\n");
    exit(-1); //直接退出，并且将退出状态设置为-1
  }

  return 0;
}

emacs@ubuntu:~/c$ alias gtc
alias gtc='gcc -Wall -g -o'
emacs@ubuntu:~/c$ gtc process.x process.c
emacs@ubuntu:~/c$ ./process.x 
this is child, pid is :7588, my father pid is 7587
1 loop...(there are 4 times left)
this is the parent process(7587),wait for child(7588)...
2 loop...(there are 3 times left)
3 loop...(there are 2 times left)
4 loop...(there are 1 times left)
5 loop...(there are 0 times left)
this is the father process, my pid is 7587, child process is 7588, the wait return value is 0 
emacs@ubuntu:~/c$