CSC231 Bash Lab 1

--D. Thiebaut (talk) 17:04, 2 February 2017 (EST)

---

This tutorial introduces the basic navigation commands, and will show you how to create directories (folders) and move in and out of them. I have used and adapted much of the information that is presented in several excellent tutorials:

• http://linuxcommand.org/
• http://ryanstutorials.net/linuxtutorial/

Switching to the Bash Shell

Skip this part if you have already switched to the Bash shell...
By default, your student account using the shell called tcsh. We will be using another shell that is more friendly: bash.
Open a terminal or console window and connect to aurora.smith.edu with your class account. Here we assume that your class account is of the form cs231a-xx where xx are two unique letters associated with your personal account.
Run this command at the Linux prompt:

setup231.sh

What this does is to copy the a file from your instructors account (~cs231a) into your account (~cs231a-xx). This file is read automatically every time you login to your account and will set the shell to bash.

• logout of your account
• log back in. You should see something like this:

cs231a-xx@aurora.smith.edu's password: 
Welcome to Linux Mint 17 Qiana (GNU/Linux 3.13.0-24-generic x86_64)

Welcome to Linux Mint
* Documentation:  http://www.linuxmint.com
Last login: Thu Feb  2 16:59:49 2017 from 131.229.199.140
bash: setenv: command not found
cs231a-xx@aurora ~ $ 

Backing up your files

Just in case you mess up and erase files in your account that you'd like to keep, you will make an archive of all your files and save it in your instructor's account:

cd
tar -czvf backup.tgz *
rsubmit backup backup.tgz

That's it! Your instructor should now have a copy of all the files you may have created in your home account, and in case you delete some by mistake, they should be recoverable.

Creating Subdirectories

We are going to create the following tree of directories shown below. Note that you do not need to create the cs231a-xx folder, as it is by default already there: it's your home directory.

Type in the following commands to create the tree and put files in the different folders. Note: you will use the getcopy command that is not a Linux command, but rather a program created for the CS department accounts.

  rm lab1
  mkdir lab1
  mkdir hw1
  mkdir misc
  ls

You should see the 3 directories in your account.

Let's go in the misc folder:

  cd misc
  ls

Let's create 2 subdirectories there: demo and pictures:

  mkdir demo
  mkdir pictures
  ls

Navigating the Subdirectories

Now, let's go "up" one level and look at what we have created and what they contain (the subdirectories should all be empty at this point):

  cd ..
  ls
  ls hw1
  ls lab1
  ls misc
  ls misc/demo

Let's go into lab1 and put the file prog1.asm there. We'll get prog1.asm from the instructor's handout directory:

  cd lab1
  getcopy prog1.asm
  ls

Now let's go into hw1, which is at the same level as lab1 and put prog2.asm into it:

  cd ../hw1
  getcopy prog2.asm
  ls
  cat prog2.asm 

Same thing with misc and prog3.asm

  cd ../misc
  cd demo
  getcopy prog3.asm

and finally we'll get prog4.asm and put it into pictures.

  cd ../pictures
  getcopy prog4.asm
 

A view from the Home Directory

Let's go back "home" and see if we can see the different prog*.asm files without actually "cd"-ing to the folders:

To go "home" we simply type:

cd

And we can look at the contents of the different sub- and sub-sub-directories:

ls lab1
ls hw1
ls misc
ls misc/demo
ls misc/pictures 

You should have seen all 4 prog*.asm files. Yes?

Challenge #1: A New Directory Tree

Let's remove all the new files and subdirectories you have just created. In Linux, "removing" means "deleting." The "rm" command deletes a file, while "rmdir" removes an empty directory. You have to delete all the files and subdirectories inside a directory before deleting it.

 cd
 rm hw1/prog2.asm 
 rm lab1/prog1.asm 
 rm misc/demo/prog3.asm 
 rm misc/pictures/prog4.asm 
 rmdir misc/pictures/
 rmdir misc/demo/
 rmdir misc
 rmdir lab1
 rmdir hw1

Now, using similar commands as the ones you used in the previous section, create the following directory tree:

Challenge 1: Verification

You can check wether you have created the correct tree by typing the following command (too evolve for us to try to understand it today) which will look for all the file with a ".asm" extension in your account:

find . -name "*.asm" -print

If you have created your tree correctly, you should get

./hws/hw1/prog1.asm
./hws/hw1/prog2.asm
./misc/demo/pictures/prog3.asm
./misc/demo/pictures/prog4.asm

(You may have other files that you had created before today listed. That's fine, as long as the 4 lines above appear in the output.)

Copying Files

cp is the copy command. It simply makes a duplicate of a file somewhere in the tree.
Run the command makeLab1Tree.

makeLab1Tree

It will create a new subdirectory tree in your account, with the HWorks as the top subdirectory. Explore it with the cd command and go up and down the tree of subdirectories. Verify that it contains 4 different subdirectories and 4 assembly programs:

./HWorks/hw1/prog1.asm
./HWorks/hw2/prog2.asm
./HWorks/hw4/prog4.asm
./HWorks/hw3/prog3.asm

We are now going to use cp (for copy) prog2.asm, prog3.asm, and prog4.asm to the HWorks directory.

cd 
cd HWorks
cp hw1/prog1.asm  .
cp hw2/prog2.asm  .
cp hw3/prog3.asm  .
cp hw4/prog4.asm  .

Take a look at your current directory with ls, and verify that you now have your 4 programs in one place.

Moving Files

Assume that you didn't want copies of the files but you wanted to move them from the hw1, hw2, hw3, and hw4 directories to HWorks. You need to use mv (for move) rather than cp.

Let's remove the asm files currently in HWorks:

cd 
cd HWorks
rm prog*.asm 

The * character is called a wild-char and matches any string. So prog*.asm will match prog1.asm, prog2.asm, prog3.asm and prog4.asm. So one command will remove all 4.

Now move the files from the hw1, hw2, hw3, and hw4 directories to HWorks:

mv hw1/prog1.asm  .
mv hw2/prog2.asm  .
mv hw3/prog3.asm  .
mv hw4/prog4.asm  .

Verify that all 4 assembly programs are now in HWorks, and have disappeared from hw1, hw2, hw3, and hw4.

Challenge #2: Secret Message

Run the program makeLab1Tree2. It will create a new tree of subdirectories in your home.

Explore the tree and see if you find a mystery file. Its contents has important information for you!