IT 244: Introduction to Linux/Unix

IT 244: Introduction to Linux/Unix
Homework 8

Due

Sunday, November 3rd at 11:59 PM

What You Need to Do

Create the script hw8.sh with Unix commands that will do what is described in the steps below
This file must be in an hw8 directory under your hw directory

Setup

From your home directory go to your it244 directory
```
cd it244
```
Go to your hw directory
```
cd hw
```
Create an hw8 directory
```
mkdir hw8
```
Enter this new directory
```
cd hw8
```
Create hw8.sh
```
nano hw8.sh
```

Specification

Create the file hw8.sh inside your hw8 directory using nano
Write the Unix command to perform the action specified by each step
Be sure to write a Step comment before the Unix commands for each step

Perform the following actions
- Run ls on a file that does not exist
- Run ls on the same file, but redirect Standard Error to /dev/null
- Run ls on the same file, but redirect Standard Error to errors.txt
- Print errors.txt to the terminal
The commands above do not have to be on the same line.
Using 3 commands on the same command line
- Go to your home directory
- Run ls
- Return to your hw8 directory
For this step you will write two command lines.
Copy bother10.sh from /home/ghoffman/course_files/it244_files to your hw8 directory.
This will be your first command line.
Write a single command line that
- Runs bother10.sh sending the output to /dev/null, but does this in the background
- Runs bother10.sh sending the output to /dev/null, but does this in the background
- Runs bother10.sh sending the output to /dev/null, but does this in the background
- Runs ps, but in the foreground
All of the above will be your second command line.
Using pushd to go to new directories and popd to return to previous directories, do the following.
- Go to your home directory
- Show your position in the filesystem
- Go to my home directory
- Show your position in the filesystem
- Return to your home directory
- Show your position in the filesystem
- Return to your hw8 directory
- Show your position in the filesystem
Do the following
- Create the local variable foo and assign it the value "FOO"
- Create the global variable bar and assign it the value "BAR"
- Write a single command that will print the values of foo and bar
Do the following
- Copy print_foo_bar.sh from /home/ghoffman/course_files/it244_files to your hw8 directory
- Run print_foo_bar.sh
The value of foo will not print because it is local to the login shell and cannot be seen in the subshell running print_foo_bar.sh.
Do the following
- Create the global variable my_city and assign it the name of the town you live in
- Write an echo statement that uses my_city to tell me where you live.
  If I were to run this command the outout would be
```
I live in Somerville
```
There is a keyword shell variable which the shell uses to find the directory that contains the executable file to run a command.
Print the value of this varable.
Print the value of the keyword shell variable whose value is the absolute pathname of your default shell.
Run a command that will show you all your global variables.

Testing

There are two tests that your should run on your script
The first test checks for Unix errors
Run bash on your script like this
```
bash hw8.sh > /dev/null
```
This will run your script but will only show error messages

You can ignore the following error message

ls: cannot access 'xxxx': No such file or directory

If you see nothing, your script has passed this test
The second test checks your Step comments

Run it like this

~ghoffman/code/it244_code/testing_scripts_it244/step_comment_check.sh

If your Step comments are wrong you will lose points