从 exec 获取输出 [英] Grabbing output from exec

问题描述

我正在尝试编写一个 C 程序来获取命令输出，然后我会将其传递给另一个程序.

I'm trying to write a C program that grabs command output and then i'll be passing that to another program.

我遇到了一个问题，我不知道如何获取命令输出并存储它.以下是我所拥有的样本

I'm having an issue, I cant work out how to get the command output and store it. Below is a sample of what I have

if(fork() == 0){
   execl("/bin/ls", "ls", "-1", (char *)0);
   /* do something with the output here */
}
else{
    //*other stuff goes here*
}

所以基本上我想知道是否有任何方法可以从execl"获取输出并将其传递给其他东西(例如，通过将其存储在某种缓冲区中).

so basically im wondering if there is any way i can get the output from the "execl" and pass it to some thing else (e.g. via storing it in some kind of buffer).

建议会很棒.

推荐答案

您必须使用 pipe() 创建从父进程到子进程的管道.然后您必须使用 dup 或 dup2 将 standard 输出 (STDOUT_FILENO) 和 error output (STDERR_FILENO) 重定向到管道，并在父进程中，从管道中读取.它应该可以工作.

You have to create a pipe from the parent process to the child, using pipe(). Then you must redirect standard ouput (STDOUT_FILENO) and error output (STDERR_FILENO) using dup or dup2 to the pipe, and in the parent process, read from the pipe. It should work.

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

#define die(e) do { fprintf(stderr, "%s
", e); exit(EXIT_FAILURE); } while (0);

int main() {
  int link[2];
  pid_t pid;
  char foo[4096];

  if (pipe(link)==-1)
    die("pipe");

  if ((pid = fork()) == -1)
    die("fork");

  if(pid == 0) {

    dup2 (link[1], STDOUT_FILENO);
    close(link[0]);
    close(link[1]);
    execl("/bin/ls", "ls", "-1", (char *)0);
    die("execl");

  } else {

    close(link[1]);
    int nbytes = read(link[0], foo, sizeof(foo));
    printf("Output: (%.*s)
", nbytes, foo);
    wait(NULL);

  }
  return 0;
}

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