= How to Code in a Terminal Window

When you want to develop programs, e.g. in Python, on a server, the easiest connection option usually is via `ssh` access and the [https://en.wikipedia.org/wiki/Command-line_interface command line mode] in a [https://en.wikipedia.org/wiki/Terminal_emulator terminal window].

In case, you are not used to working in a terminal, we have gathered a small set of recommendations and tutorial links. The examples will be using the NLP lab server [https://aurora.fi.muni.cz aurora] as an example.

* for the **primary access**, see the information for various OSes directly at https://aurora.fi.muni.cz
* for **basic navigation** once you are logged in, see the [https://ubuntu.com/tutorials/command-line-for-beginners#3-opening-a-terminal Ubuntu tutorial for working in terminal]. 
* for **easy repeated access**, you should setup a ''SSH key authorization'', see the simple [https://aurora.fi.muni.cz/ssh-keys.html aurora SSH keys tutorial].
* choose and learn (at least) one **in-terminal text editor**. An easy
  option is the [https://www.nano-editor.org/dist/v2.2/nano.html nano editor] - just run `nano source.py` and start editing, save with
  `Ctrl+S`, exit with `Ctrl+X`. An advanced option is the
  [http://www.vim.org/ vim editor] - we suggest e.g. the
  [https://missing.csail.mit.edu/2020/editors/#vim MIT course VIM intro]
  for an initial engagement with `vim`. When you start `vim source.py`, you
  should press `i` to edit the text and `Esc`, `:w<Enter>` to save changes
  or `:q!<Enter>` to discard changes.
* when developing a program, e.g. in Python, we suggest to **work in
  multiple terminal windows**. For each window start a separate
  terminal connection to the server (SSH key authorization comes very
  handy here), change to the same directory on the server and use
  for example:
  - one window for source code editing. Do not exit the editor, just save
    changes and test in another window.
  - one window for running the code and inspecting the results.
  - one window for running a debug (e.g. via `python -mpbd source.py`).
  - one window for working with auxiliary files, e.g. edit testing
    data.
* for **easy data+code sharing** consider using an independent Git
  repository, e.g. https://gitlab.fi.muni.cz. In that case, you shall
  store all your source codes and data files in [https://gitlab.fi.muni.cz/ Gitlab]
  and just `git clone` the repository to the server. Use `git add`, `git commit -a`
  and `git push` to promote changes that you make on the server
  back to [https://gitlab.fi.muni.cz/ Gitlab]. Use `git pull` to update the
  previously cloned repository in the server directory with changes made
  elsewhere. See e.g. the 
  [https://missing.csail.mit.edu/2020/version-control/#repositories MIT Git intro]
  for other details about working with Git.
* how to **discover and fix errors** - we suggest two standard options:
  `logging` and `pdb` debugging:
  - **logging** is based on standard Python
    [https://docs.python.org/3/library/logging.html logging library]. It
    allows to supplement your program with messages of various levels of
    verbosity which can be turned on and off. A simple program may look
    like 
    {{{#!python
    import logging

    logging.basicConfig( level=logging.DEBUG, format="%(message)s")

    logging.info("Program starting")
    a = 2
    b = 2
    logging.debug(f"About to sum {a} and {b}")
    logging.info(f"The result is {a+b}")
    }}}
  - **pdb debugging** is run from the command line with including the specific
    `pdb` module. Start the debugging via `python -mpdb source.py`, then
    use line-based commands as described in the 
    [https://missing.csail.mit.edu/2020/debugging-profiling/#debuggers MIT code page].
    Command `q` quits the debugger.
* if you are curious enough to get to a **terminal pro level**, we suggest
  to go through the full MIT course [https://missing.csail.mit.edu/ The Missing Semester of Your CS Education].