Thread: Redirecting stdin - freopen alternative

  1. #1
    Registered User
    Join Date
    Nov 2010

    Question Redirecting stdin - freopen alternative

    I'm currently redirecting in a non-portable manner the standard input as:

    freopen ("/dev/tty", "r", stdin);
    which /dev/tty always points to the user's terminal. This helps me to read from input in a non-blocking manner.

    I can perform well something like:

      while(fgets(buf, sizeof(buf), stdin))
        fputs(buf, stdout);
      freopen("/dev/tty", "rw", stdin);
      // continue with the rest of the code in a non-blocking manner
    I'm wondering what would be an alternative to freopen, perhaps using I/O multiplexing. such as select()? or a thread that blocks on reading stdin?

    Any alternative sample code would be appreciated.

    Platforms: BSDs, Linux

  2. #2
    and the hat of int overfl Salem's Avatar
    Join Date
    Aug 2001
    The edge of the known universe
    Sure, stdin is file descriptor 0, and you can use that in an fd_set passed to select()

    You might need to be careful between select detecting a single character being available, and fgets potentially blocking until a newline is entered.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

  3. #3
    Registered User
    Join Date
    Nov 2010
    Could you elaborate a little bit more about using select() instead of freopen? Or how would that apply on the above case? Thanks for your reply.

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