IT 244: Introduction to Linux/Unix

IT 244: Introduction to Linux/Unix
Class 16 Exercise

Go to your home directory
```
cd
```
Make sure you are in your home directory
```
pwd
```
Look for any bash startup files
```
ls -a .bash*
```
You should at least see .bash_history.
Create a .bash_profile startup file
```
nano .bash_profile
```
Enter the following line:
```
ex=~/it244/ex
```
There must not be any spaces on either side of the =.

You have just created the variable ex with the value of ~/it244/ex.
Save your changes and quit nano
Try to use this new variable
```
echo $ex
```
echo prints a blank line, because .bash_profile ran when you first logged in.

When .bash_profile ran, ex was not defined in .bash_profile.

It has not been run again since you made the changes.
Run .bash_profile in your current shell
```
source .bash_profile
```
Now try to use the new variable
```
echo $ex
```
Use this new variable to go to your ex directory inside your it244 directory
```
cd $ex
```
Verify your current location
```
pwd
```

Go back to your home directory
```
cd
```
Create a .bashrc file
```
nano .bashrc
```
Notice that this is a different file than .bash_profile.
Enter the following line in the file
```
PS1='--> '
```
Again, there must be no spaces on either side of the =.
Save your changes and quit nano
Create a subshell
```
bash
```
Notice that your prompt has changed.

That is because you changed the prompt variable PS1 in your .bashrc file.

When you created this interactive non-login shell, all the commands in .bashrc were executed.

.bashrc changed the value of PS1, giving you a new prompt.
Look at your running processes
```
ps
```
The first bash process is your login shell.

The second is your current shell.
Leave the subshell
```
exit
```
Notice that your prompt now has returned to normal.
Run ps again
```
ps
```
You have only one bash process running.

This means you are back in you login shell.

Find the file that will be run when you use ls
```
which ls
```
You get an absolute pathname, so ls is not a built-in.
Find the file that will be run when you use cat
```
which cat
```
cat is also not a built-in.
Find the file that will be run when you use bg
```
which bg
```
which returns nothing because bg is a built-in command.

This means the code for this command is contained within the shell itself.
Find the file that will be run when you use fg
```
which fg
```
fg is also a built-in command.

Go to your home directory
```
cd 
```
Go to your ex16 directory
```
cd it244/ex/ex16
```
Make sure you are in the right directory
```
pwd
```
Run the script make_foo.sh
```
~ghoffman/course_files/it244_files/make_foo.sh
```
This script will create some files that you will use in the remainder of this exercise.
Look at the files created by running the script
```
ls -l
```
Run a long listing on using a single character and *
```
ls  -l  f*
```
You only have to enter as many characters as are needed to distinguish the files you want from the files you don't want.
Run a long listing using the * metacharacter
```
ls  -l  foo1*.txt
```
Run a long listing using more than one *
```
ls  -l  f*2*
```
You can use multiple instances of metacharacters.

Run a long listing using the ? metacharacter
```
ls  -l  foo?.txt
```
Notice that foo.txt and the files foo10.txt through foo29.txt do not appear in the listing.
Run another long listing the ? metacharacter
```
ls -l foo2?.txt
```
Notice that you only print the files foo20.txt to foo29.txt
Run a long listing using two ? metacharacters
```
ls -l foo??.txt
```
Notice that you now you see the files foo10.txt to foo29.txt

Use the bracket metacharacters to select foo files 1 through 3
```
ls  -l  foo[123].txt
```
Use a range to list foo files 1 through 5
```
ls  -l  foo[1-5].txt
```
List all numbered foo files except 5 and 10
```
ls  -l  foo[1-46-9].txt
```
List the same files as above using a shorter search string
```
ls  -l  foo[!05].txt
```
Use the bracket metacharacters to select foo files 14 through 16
```
ls  -l  foo1[456].txt
```
Use a range to list foo files 16 through 19
```
ls  -l  foo1[6-9].txt
```
List all numbered foo2 files except 20 and 25
```
ls  -l  foo2[1-46-9].txt
```
List the same files as above using a shorter search string
```
ls  -l  foo2[!50].txt
```

Make sure you are in your ex16 directory
```
cd ~/it244/ex/ex16
```
Create the script ex16.sh
```
nano  ex16.sh
```
Write into this file the commands from certain sections above

Copy the commands from the section titled Built-in Commands up to and including the section Using More Than One Meta-character
Save this file

Save and quit.
Make this file executable
```
chmod 755 ex16.sh
```
Run this script looking for error messages
```
./ex16.sh > /dev/null
```
Running ex16.sh this way will only print error messages.

If you see nothing your script has no Unix errors.

If you find any errors, fix them.
Test your script
```
~ghoffman/it244_test/ex16.sh
```
When the script asks if you are ready for more, hit Return or Enter.
Let me check your script