Question

can someone give me simple example in c, of using pipe() system call to and use ssh to connect to a remote server and execute a simple ls command and parse the reply. thanks in advance,..

Answer 1

int main()
{
    const char host[] = "foo.example.com";  // assume same username on remote
    enum { READ = 0, WRITE = 1 };
    int c, fd[2];
    FILE *childstdout;

    if (pipe(fd) == -1
     || (childstdout = fdopen(fd[READ], "r")) == NULL) {
        perror("pipe() or fdopen() failed");
        return 1;
    }
    switch (fork()) {
      case 0:  // child
        close(fd[READ]);
        if (dup2(fd[WRITE], STDOUT_FILENO) != -1)
            execlp("ssh", "ssh", host, "ls", NULL);
        _exit(1);
      case -1: // error
        perror("fork() failed");
        return 1;
    }

    close(fd[WRITE]);
    // write remote ls output to stdout;
    while ((c = getc(childstdout)) != EOF)
        putchar(c);
    if (ferror(childstdout)) {
        perror("I/O error");
        return 1;
    }
}

Note: the example doesn’t parse the output from ls, since no program should ever do that. It’s unreliable when filenames contain whitespace.