(other-commands)=
# Other UNIX commands[^hs]

[^hs]: A colleague of mine once said, "The commands in UNIX are
    the initials of the people that the designers went to high
    school with."

    A good story, but it's not true. The reality is that when
    [UNIX was first developed](https://en.wikipedia.org/wiki/History_of_Unix)
    in the 1960s, computers had six orders of magnitude less memory
    than they do today. The space for internal tables containing items like
    command names was at a premium. From then to now, UNIX command names
    tend to be terse.
    
-   *To copy a file:* use the `cp` command.[^f8]

    For example, to copy the file `CreateSubdirectories.C` from the
    directory `~seligman/root-class` to your current working directory,
    type:

        > cp ~seligman/root-class/CreateSubdirectories.C $PWD

    In UNIX, `$PWD` means the results of the `pwd` command.[^f9]

[^f8]: Over the years, as students began to use laptops, I noticed
    that many of them had an interesting misconception: The `cp`
    command copies a file from one place to another on the same
    computer. It does *not* copy a file from a remote server to your
    laptop! For that you use `scp`; use `man scp` to learn more. Note
    that if you're working on a remote server such as the ones at
    Nevis, there's no reason to use `scp` for this tutorial.

[^f9]: A period (`.`) is the usual abbreviation in UNIX for "the
    current directory" (did you remember that `..` means "the
    directory above this one"?) but many students missed the period the
    first time I taught this class.

-   *To look at the contents of a text file:* Use the {command}`less`
    command.[^f10]

    This command is handy if you want to quickly look at a file without
    editing it. To browse the contents of file `CreateSubdirectories.C`,
    type:

        > less CreateSubdirectories.C

    While `less` is running, type a space to go forward one screen, type
    `b` to go backward one screen, type `q` to quit, and type `h` for
    a complete list of commands you can use.

[^f10]: If the name is confusing: the {command}`less` command was created as a
    more powerful version of the {command}`more` command.

-   *To get help on any UNIX command:* type `man <command-name>`

    While `man` is running, you can use the same navigation commands as
    `less`. For example, to learn about the `less` command, type:

        > man less

(rm)=
-   *To delete a file:* Use the {command}`rm` command.[^notrash] For example:

        > rm CreateSubdirectories.C

[^notrash]: **Super-duper warning: There is no Trash folder or "undo"
    operation in command-line UNIX!** If you use {command}`rm` on a file
    and later realize that was a mistake, there's pretty much nothing 
    you can do except re-create the file from scratch. 

    Be warned: A notorious UNIX prank is for someone to get you to type
    `rm -rf ~` which performs an unrecoverable delete of all of your
    files without any warning. Don't fall for it!

(emacs)=
-   *To edit a file:* I suggest you use `emacs`.[^f11] For example, to
    edit the file CreateSubdirectories.C:

        > emacs CreateSubdirectories.C

    This may appear to "lock up" your UNIX window. If this is an issue,
    either create a new UNIX window or learn about [ampersands at the end of
    a command
    line](https://bashitout.com/2013/05/18/Ampersands-on-the-command-line.html).

    The `emacs` environment is complex, and you can spend a lifetime
    learning it.[^f12] For now, just use the mouse to move the cursor and
    look at the menus. When you get the chance, I suggest you take the
    `emacs` tutorial by selecting it under the {guilabel}`Help` menu.[^whyemacs]

[^f11]: If you\'re already familiar with another text-based UNIX editor,
    such as `nano` or `vim`, you can use it instead.

    If you're not using a remote UNIX server and you're editing files on
    your laptop, make sure you're using a plain-text editor. If you use
    an editor whose default mode is to *not* save files in plain text
    (Microsoft Word is one example; the poorly-named TextEdit on the Mac
    is another) you're going to get confused. If you don't already have
    such an editor, I suggest
    [Notepad++](https://notepad-plus-plus.org/) on MS-Windows and the
    free version of [BBEdit](https://www.barebones.com/products/bbedit/)
    for the Mac.

    What do I mean by "you're going to get confused" in the previous
    paragraph? When I taught Python to my father, he tried to use
    Microsoft Word to edit code. He didn't understand why you couldn't
    apply a bold or italic font style to text in a program. He also
    often forgot to use `Save As...` and switch the file format to
    `Plain Text`, so his code was saved as a Word document.

    Of course, you're not my father; otherwise I'd ask you if I could
    stay out late this Saturday. You may find Word is the best
    plain-text editor for you.


[^whyemacs]: As a final aside: There's
    [lots](https://www.redhat.com/sysadmin/3-text-editors-compared) of
    [debate](https://unkertmedia.com/emacs-vs-nano-vs-vim/) over which
    is the best UNIX editor: `emacs`, `vim`, or `nano`. I'm aware that
    `emacs` is now the minority choice. I recommend `emacs` because
    it's the one I always use, for two reasons:

    - As I discuss on the next web page, the keyboard commands are useful
      on the UNIX command line.

    <p />

    - Emacs has a large number of
      [modes](https://www.gnu.org/software/emacs/manual/html_node/emacs/Modes.html)
      that make it easier to edit code. This includes syntax
      highlighting and auto-indentation.

      If you're used to Python, the notion of auto-indenting will seem
      trivial to you: You have to indent your code anyway. For a
      language like C++, emacs can automatically indent code to make
      it more readable. This helps a lot when someone sends you a code
      file that's an unreadable mish-mash.

      These modes are language-dependent; e.g., the syntax
      highlighting and indentation are different when you're editing a
      C++ file, a shell script, or a web file.  To me, this more than
      makes up for any perceived deficiencies between emacs and vim.

[^f12]: I've spent two of your lifetimes already, and the class has just
    started!

:::{tip} 
Are you quitting <tt>emacs</tt> after you change a file, only to start up the
editor again a moment later? Hint: look at {menuselection}`File`. If you're
editing many files, try opening them all with {menuselection}`File --> Open File`
and switch between them using {menuselection}`Buffers`. Remember to use
{menuselection}`File --> Save` once in a while.

Learn how to cut and paste in whatever editor you use. If you don't,
you'll waste a lot of time typing the same things over and over again.
:::

:::{figure-md} real_programmers-fig
:class: align-center

<img src="https://imgs.xkcd.com/comics/real_programmers.png" alt="xkcd real_programmers">

<http://xkcd.com/378> by Randall Munroe. 
If you're feeling bored, type `Meta-x butterfly` in emacs and see what
happens.
:::