Question

我试图理解父母和孩子之间的沟通。免责声明：以下是我的教授在课堂上提供的用于理解进程间通信的示例代码。我的主要弱点是文件描述符。我知道pipe（int array [2]）使得std in和array [1]的数组[0] = fd为std out。但这两者之间的沟通情况如何呢？我对CS很新。谢谢！

/*
 * This program demonstrates the use of pipes for interprocess communication.
 * The parent process creates a pipe using the "pipe" system call. It then
 * creates a child process and passes the child a file descriptor for one side
 * of the pipe. It then writes a name to its side of the pipe and waits for the
 * child to print a message incorporating the name.
 *
 * Before you attempt to run this program, be sure you've compiled the program
 * named "hw3b.c" and have the executable in a file named "hw3b".
 */

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

/*
 * The name of the file we plan to run.  It's here in a define so that we can
 * change it easily
 */
#define CHILDPROCNAME "hw3b"

/*
 * The behavior of main() is specified by the previous comment
 */

int main(char* argv)
{
    // store the ids of the two file descriptors that serve as the pipe
    int mypipe[2];

    // make the pipe
    pipe(mypipe);

    // child code:
    if (fork() == 0) {
        // execv requires us to create a full invocation, consisting of the
        // string name of the program to run, a string for each command-line
        // argument, and then a null string.  We store all that in this array of
        // strings
        char* myargv[3];

        // we use this to turn an int into a string
        char buf[50];

        //  set up the name of the program to run
        myargv[0] = calloc(strlen(CHILDPROCNAME) + 1, sizeof(char));
        strcpy(myargv[0], CHILDPROCNAME);

        // write one of the pipe's fds to the second parameter
        sprintf(buf, "%d", mypipe[0]);
        myargv[1] = calloc(strlen(buf) + 1, sizeof(char));
        strcpy(myargv[1], buf);

        // third param is null
        myargv[2] = 0;

        // switch to child process
        execv(CHILDPROCNAME, myargv);

        // NB: this should use fprintf and write to stderr
        printf("Uh oh, execv didn't work!\n");

       // crash on failure
       exit(-1);
    }

    // parent code
    else {
       // status variable for storing the result of waitpid
       int status;

       // Send a string across the pipe to the child process
       write(mypipe[1], "Kerry", strlen("Kerry"));

       // wait for the child process to finish
       waitpid(-1, &status, 0);

       // NB: we should use status!
    }

    // close our half of the pipe
    close(mypipe[1]);
}

Answer 1

它只是用childproc替换程序中的p1。他可能意味着它取决于价值，p1。

子管道进程间通信管道

1 个答案: