| Ptyprocess |
| ========== |
| |
| .. include:: ../README.rst |
| |
| Contents: |
| |
| .. toctree:: |
| :maxdepth: 2 |
| |
| api |
| |
| What is a pty? |
| -------------- |
| |
| A pty is a kernel-level object which processes can write data to and read data |
| from, a bit like a pipe. |
| |
| Unlike a pipe, data moves through a single pty in both directions. When you use |
| a program in a shell pipeline, or with :class:`subprocess.Popen` in Python, up |
| to three pipes are created for the process's standard streams (stdin, stdout |
| and stderr). When you run a program using ptyprocess, all three of its standard |
| streams are connected to a single pty: |
| |
| .. image:: images/pty_vs_popen.png |
| |
| A pty also does more than a pipe. It keeps track of the window size (rows and |
| columns of characters) and notifies child processes (with a SIGWINCH signal) |
| when it changes. In *cooked mode*, it does some processing of data sent from the |
| parent process, so for instance the byte ``03`` (entered as Ctrl-C) will cause |
| SIGINT to be sent to the child process. |
| |
| Many command line programs behave differently if they detect that stdin or stdout |
| is connected to a terminal instead of a pipe (using |
| `isatty() <http://linux.die.net/man/3/isatty>`_), because this normally means |
| that they're being used interactively by a human user. |
| They may format output differently (e.g. ``ls`` lists files in columns) |
| or prompt the user to confirm actions. |
| When you run these programs in ptyprocess, they will exhibit their 'interactive' |
| behaviour, instead of the 'pipe' behaviour you'll see using ``Popen()``. |
| |
| .. seealso:: |
| |
| `The TTY demystified <http://www.linusakesson.net/programming/tty/>`_ |
| Detailed article by Linus Akesson |
| |
| Indices and tables |
| ================== |
| |
| * :ref:`genindex` |
| * :ref:`modindex` |
| * :ref:`search` |
| |
