# Other UNIX commands

-   *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]: 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 `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 `less` command was created as a
    more powerful version of the `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

(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 **Help** menu.

[^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.

    On a Mac, `emacs` is built-in and you can use it from within
    Terminal. You'll get the screen-based version instead of the
    window-based version; do *not* put & after the command. You'll also
    need to take the tutorial immediately, as suggested in `emacs`'
    "Welcome" screen, since the editing keypresses for the screen-based
    `emacs` are not obvious.

[^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 the **File** menu. If you're
editing many files, try opening them all with **File->Open File\...**
and switch between them using the **Buffers** menu. Remember to use
**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.
:::