Fun with Linux

From Education

Creating and Cat-ing

Now that you've heard the Introduction to Linux presentation, it's time to practice some basic Linux commands. First, remember the rule of thumb - know thyself! If you ever forget, just type whoami. (Try this now.) It's also helpful to know where you are. pwd stands for print working directory, and it will show you.

Let's make a folder to play around in: do this with the command mkdir <directoryname>. Once you've done that, use ls to see that your directory has been created, then move into it with cd <directoryname>.

kwanous@eyrie:~$ mkdir funwithlinux
kwanous@eyrie:~$ ls
funwithlinux  hosts
kwanous@eyrie:~$ cd funwithlinux/

Let's create a file to play around with. To create an empty file in Linux, use the command touch <filename>. For example,

kwanous@eyrie:~/funwithlinux$ touch mynewfile
kwanous@eyrie:~/funwithlinux$ ls
mynewfile

Right now this file has nothing in it. We can verify this with the cat command. Cat, short for concatenate, prints the contents of a file to the screen. If you type cat <filename>, nothing should be printed. Let's add something to the file. To open the file in a text editor called "nano", type nano <filename>. Go ahead and type a few different lines in your file, something like the following, and then save it.

Hi!  My name is Kristina.
I am having fun with Linux!
This is in my file called mynewfile.

Then use cat <filename> again. The new contents of the file should be displayed.

Copying and Moving

Let's say we want to change this file's name. The way we do this is by moving it to a new location. The syntax for this is mv <oldname> <newname>. For instance,

kwanous@eyrie:~/funwithlinux$ mv mynewfile MyNewFile
kwanous@eyrie:~/funwithlinux$ ls
MyNewFile

Notice that the original copy is gone. What if we wanted to keep the original and make changes to the new one? To make a copy of a file, use cp <original> <newfilename>. Go ahead and make mynewfile again using cp. Use ls to make sure both mynewfile and MyNewFile are in your directory.

Let's change mynewfile to make sure that it and MyNewFile are really two separate files. Use nano to change mynewfile and save it. Then cat both of your files. (Is Linux case sensitive? How do you know?)

We can also move files to a different directory. Create a new directory called firstexample and then move the files into this directory using either an absolute or relative location.

Relative positioning:

kwanous@eyrie:~/funwithlinux$ mv mynewfile firstexample/

Absolute positioning:

kwanous@eyrie:~/funwithlinux$ mv mynewfile ~/kwanous/funwithlinux/firstexample/

Ls and Wildcards

Now, let's create more files to play around with. Use touch to create the files pickel, pear, peach, apple, and prune. Rather than typing these in one line at a time, you can put them all on one line like this:

kwanous@eyrie:~/funwithlinux$ touch pickel pear peach apple prune

Oops! I spelled pickle wrong. If you followed my example and did too, use mv to change the file name.

Typing ls will show all of the new files you've created. To see more information about the files in a list format, try ls -l. This shows all of the files in the directory you're currently in. But what if we only wanted the files that started with p? Try ls p* or ls -l p*. Is Linux case sensitive? Try ls P* to find out.

The * is called a wildcard character. What exactly does it mean? Try a few experiments to find out (like ls peach* and ls *e and ls *). How would you display the files that start with p and end with e?

Removing Files and Directories

Let's moving on to removing items. Let's remove peach. Use rm peach, then do an ls to make sure it's really gone. But what if we wanted to remove multiple files? The wildcard character works the same here as it does with ls! (Be very careful with rm *!) Go ahead and remove apple and grape with one command.

Next let's remove the directory. Try rm <directoryname>.

kwanous@eyrie:~/funwithlinux$ rm firstexample/
rm: cannot remove `firstexample/': Is a directory

What happened? rm is letting you know that this is a directory. Just like there's a special command to create directories (mkdir), there's a special command to remove directories so that people don't accidentally remove a directory thinking that it's a file. It's used as rmdir <directoryname>. Hm... if you had files in your folder like I did, it still won't work. Rmdir gives us the reason why, too.

kwanous@eyrie:~/funwithlinux$ rmdir firstexample/
rmdir: firstexample/: Directory not empty

This is a protection mechanism built in to help users not accidentally delete folders with files still in them. One way we could remove everything would be to move into the directory and then remove them. However, we can also do this without actually moving into the directory. Normally we don't specify a path to rm and it assumes that we mean in the current directory. However, we can also tell it to remove files from a directory that we're not currently in. Remove everything from the directory you made with rm <directoryname>/*. Similarly, we can do a "remote ls" to see if that command worked: ls <directoryname>. Once your directory is empty, try removing it again with rmdir.

Your Turn

Congratulations on making it through the tutorial! Time to put your directory creating, file creating, and change directory skills to work. Go ahead and create this hierarchy of files for practices, and remember the shortcuts:

• ~ for home directory
• . for the directory you're currently in
• .. for the directory above the directory you're currently in

Pets
  |---> Fish
  |       |---> Saltwater
  |       |---> Freshwater
  |
  |---> Mammals
  |       |---> Dogs
  |       |      |---> Large
  |       |      |---> Medium
  |       |      |---> Small
  |       |
  |       |---> Cats
  |              |---> Longhair
  |              |---> Shorthair
  |
  |---> Reptiles
          |---> Snakes
          |---> Turtles