Tinyhttpd 知识点

1. fork 子进程

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

int main(void)
{
    pid_t pid;
    int count = 0;
    pid = fork();
    while(1){
        if(pid < 0)
            printf("error in fork");
        else if(pid == 0){
            printf("i am the child process, my process id is %d
",getpid());
            count ++;
            printf("count is:%d
",count);
            sleep(1);
        }else{
            printf("i am the parent process,my process id is %d
",getpid());
            printf("count is:%d
",count);
            sleep(1);
        }
    }
    return 0;
}

运行结果:

i am the parent process,my process id is 8490
count is:0
i am the child process, my process id is 8491
count is:206

可以看出 子进程和 父进程之间的参数 count 不是同一个参数

├─sshd─┬─sshd───bash───pstree
        │      ├─sshd───bash───a.out───a.out
        │      └─sshd───bash

从pstree 指令中可以看出 a.out 之间的关系

[root@docker01 tinyhttpd_qf]# ps -ef|grep a.out
root      8655  7712  0 05:31 pts/3    00:00:00 ./a.out
root      8656  8655  0 05:31 pts/3    00:00:00 ./a.out
root      8694  7423  0 05:33 pts/2    00:00:00 grep --color=auto a.out

现在我把 a.out 子进程 kill 掉

发现只有 父进程在独自运行

 am the parent process,my process id is 8655
count is:0
i am the parent process,my process id is 8655
count is:0
i am the parent process,my process id is 8655
count is:0

重启 程序，然后先kill 父进程

发现只有子进程在 独立运行

 is:49
i am the child process, my process id is 8780
count is:50
i am the child process, my process id is 8780
count is:51
i am the child process, my process id is 8780
count is:52
i am the child process, my process id is 8780
count is:53
i am the child process, my process id is 8780