zoukankan      html  css  js  c++  java
  • Create process in UNIX like system

              In UNIX, as we’ve seen, each process is identified by its process identifier,
    which is a unique integer. A new process is created by the fork() system call. The new process consists of a copy of the address space of the original process. This mechanism allows the parent process to communicate easily with its child process. Both processes (the parent and the child) continue execution at the instruction after the fork(), with one difference: the return code for the fork() is zero for the new (child) process, whereas the (nonzero) process identifier of the child is returned to the parent.

             Typically, the exec() system call is used after a fork() system call by one of the two processes to replace the process’s memory space with a new program. The exec() system call loads a binary file into memory (destroying the memory image of the program containing the exec() system call) and starts its execution. In this manner, the two processes are able to communicate and then go their separate ways. The parent can then create more children; or, if it has nothing else to do while the child runs, it can issue a wait() system call to move itself off the ready queue until the termination of the child.

     eg:

    #include <sys/types.h>
    #include <stdio.h>
    #include <unistd.h>
    int main()
    {
    pid t pid;
    /* fork a child process */
    pid = fork();
    if (pid < 0) { /* error occurred */
    fprintf(stderr, "Fork Failed");
    return 1;
    }
    else if (pid == 0) { /* child process */
    execlp("/bin/ls","ls",NULL);
    }
    else { /* parent process */
    /* parent will wait for the child to complete */
    wait(NULL);
    printf("Child Complete");
    }
    }
    return 0;
    





  • 相关阅读:
    ARC 没有自动释放内存
    查看python的路径
    django 一些库
    实现点击按钮,出现隐藏布局
    蓝牙的开启以及搜索
    退出当前程序(应用)的小提示
    删除SharedPreferences的存储记忆
    BaseAdapter和SimpleAdapter的区别
    数据类型
    交互与注释
  • 原文地址:https://www.cnblogs.com/dyllove98/p/3241213.html
Copyright © 2011-2022 走看看