IT 244: Introduction to Linux/Unix

IT 244: Introduction to Linux/Unix
Class 9 Exercise

Go to your home directory
```
cd
```
Make sure you are in your home directory
```
pwd
```
Look at the permissions assigned to the contents of your home directory
```
ls -l
```
Go to my home directory
```
cd ~ghoffman
```
Make sure you are in my home directory
```
pwd
```
Look at the permissions assigned to the contents of my home directory
```
ls -l
```

Go to your ex9 directory
```
cd ~/it244/ex/ex9
```
Make sure you are in the right directory
```
pwd
```
Use nano to create the file name.txt
```
nano name.txt
```
Enter your name in this file and hit Enter

Then save the file (Control O) and exit (Control X) nano.
Look at the permissions on this file
```
ls -l name.txt
```
You have read and write permission on this file
Display the contents of name.txt
```
cat name.txt
```
You have read permission so you can run cat on it.
Open name.txt with nano
```
nano name.txt
```
You can only open the file if you have read permission.
Add the city in which you live under your name and hit Enter again

Then save the file (Control O) and exit (Control X) nano.
Display the content of the file again
```
cat name.txt
```
You have write permission so you were able to change the file.
Remove write permission from this file
```
chmod 400 name.txt
```
Look at the permissions for this file
```
ls -l name.txt
```
You are the only one who has any permissions on this file.

And all you can do it read it.
Display the contents of this file
```
cat name.txt
```
Open the file with nano
```
nano name.txt
```
Try to add Massachusetts as the third line of this file

Try to save (Control O) the file.

You can't because you do not have write permission.

Quit nano

Control X

When asked the following, press "N".

Save modified buffer (ANSWERING "No" WILL DESTROY CHANGES) ?

Look at the contents of this file
```
cat name.txt
```
Nothing has changed.
Remove all privileges from this file
```
chmod 000 name.txt
```
Look at the permissions for this file
```
ls -l name.txt
```
Try to display the contents of the file
```
cat name.txt
```
You can't because you no longer have read permission.
Try to open the file with nano
```
nano name.txt
```
You get an empty file because you do not have read permission now on the file
Quit nano
```
Control X
```
Restore the original privileges
```
chmod 644 name.txt
```
Look at the permissions for this file
```
ls -l name.txt
```
Display the contents of this file
```
cat name.txt
```
You can now run cat on the file because you have restored your read permission on the file.

Go to your ex9 directory
```
cd ~/it244/ex/ex9
```
Make sure you are in the right directory
```
pwd
```
Create a test.txt file
```
touch test.txt
```
Look at the permissions on your test.txt file
```
ls -l test.txt
```
Remove read permission for all but the owner of the file
```
chmod 600 test.txt
```
Look at the permissions on your test.txt file
```
ls -l test.txt
```
Give read and write permission to everyone
```
chmod 666 test.txt
```
Look at the permissions on your test.txt file
```
ls -l test.txt
```
Restore the original permissions
```
chmod 644 test.txt
```
Look at the permissions on your test.txt file
```
ls -l test.txt
```
Delete test.txt
```
rm test.txt
```

Go to your ex9 directory
```
cd ~/it244/ex/ex9
```
Make sure you are in you ex9 directory
```
pwd
```
Create the script ex9.sh
```
nano  ex9.sh
```
Write into this file the commands from the previous section

Only enter commands from the section chmod with Numeric Arguments.
Save this file

Save and quit.
Run this script looking for error messages
```
bash  ex9.sh > /dev/null
```
Running ex9.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/ex09.sh
```
When the script asks if you are ready for more, hit Return or Enter.
Let me check your script