重定向EXEC输出到缓冲器或文件 [英] Redirecting exec output to a buffer or file

问题描述

我正在写一个C程序中我叉（），执行exec（）和的wait（）。我想借此程序的输出I exec'ed写入到文件或缓冲区。

I'm writing a C program where I fork(), exec(), and wait(). I'd like to take the output of the program I exec'ed to write it to file or buffer.

例如，如果我Exec的 LS 我想写文件1文件2等缓冲/文件。我不认为有一种方法来读取标准输出，这是否意味着我必须使用管道？这儿有一般程序，我一直没能找到？

For example, if I exec ls I want to write file1 file2 etc to buffer/file. I don't think there is a way to read stdout, so does that mean I have to use a pipe? Is there a general procedure here that I haven't been able to find?

推荐答案

有关输出发送到另一个文件（我离开了错误检查将重点放在重要的细节）：

For sending the output to another file (I'm leaving out error checking to focus on the important details):

if (fork() == 0)
{
    // child
    int fd = open(file, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);

    dup2(fd, 1);   // make stdout go to file
    dup2(fd, 2);   // make stderr go to file - you may choose to not do this
                   // or perhaps send stderr to another file

    close(fd);     // fd no longer needed - the dup'ed handles are sufficient

    exec(...);
}

有关输出发送到管道，所以你就可以读取输出入缓冲区：

For sending the output to a pipe so you can then read the output into a buffer:

int pipefd[2];
pipe(pipefd);

if (fork() == 0)
{
    close(pipefd[0]);    // close reading end in the child

    dup2(pipefd[1], 1);  // send stdout to the pipe
    dup2(pipefd[1], 2);  // send stderr to the pipe

    close(pipefd[1]);    // this descriptor is no longer needed

    exec(...);
}
else
{
    // parent

    char buffer[1024];

    close(pipefd[1]);  // close the write end of the pipe in the parent

    while (read(pipefd[0], buffer, sizeof(buffer)) != 0)
    {
    }
}

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