Re: Help on pipe

[David Lee <live4thee@gmail.com>]

On Fri, Jul 10, 2009 at 2:22 PM, Ardhan Madras<nightdecoder@gmail.com> wrote:
> Hi,
>
> I'm writing pipe demo:
>
> #include <sys/types.h>
> #include <sys/wait.h>
> #include <unistd.h>
> #include <stdio.h>
> #include <string.h>
>
> int main(void)
> {
>  pid_t pid;
>  int fds[2], ret;
>  const char *sort = "/usr/bin/sort";
>  char *argv[2] = { "sort", NULL };
>
>  ret = pipe(fds);
>  if (ret == -1) {
>    perror("pipe");
>    return -1;
>  }
>  pid = fork();
>  if (pid == -1) {
>    perror("fork");
>    return -1;
>  }
>
>  if (pid == 0) {
>    int ret;
>
>    close(fds[1]);
>    dup2(fds[0], STDIN_FILENO);
>
>    ret = execve(sort, argv, NULL);
>    if (ret == -1) {
>      perror("execve");
>    }
>    close(fds[0]);
>    _exit(0);
>  }
>  else {
>    FILE *stream;
>
>    close(fds[0]);
>    stream = fdopen(fds[1], "w");
>    if (!stream) {
>      perror("fdopen");
>      return -1;
>    }
>    fprintf(stream, "this\n");
>    fprintf(stream, "means\n");
>    fprintf(stream, "war\n");
>    fflush(stream);
>    waitpid(pid, &ret, 0);
>    close(fds[1]);
>  }
>  return 0;
> }
>
> I want to send parent's data to the child as "sort" input, i don't
> know why sort doesn't receive the data. Did i made mistake here?
>
> Thanks before.
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>

The sort program is waiting for an EOF (^D).

--- sort.c.orig 2009-07-10 15:54:36.000000000 +0800
+++ sort.c      2009-07-10 15:53:35.000000000 +0800
@@ -49,6 +49,7 @@
                fprintf(stream, "means\n");
                fprintf(stream, "war\n");
                fflush(stream);
+              fclose(stream);
                waitpid(pid, &ret, 0);
                close(fds[1]);
        }


-- 
Thanks,
Li Qun
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