IT 244: Introduction to Linux/Unix

IT 244: Introduction to Linux/Unix
Class 12 Exercise

Make sure you are in the ex12 directory
```
pwd
```
Copy the program repeat.sh from my course_files/it244_files directory to your ex12 directory
```
cp  ~ghoffman/course_files/it244_files/repeat.sh  .
```
Copy the text file five_lines.txt from the course_files/it244_files directory to your ex12 directory
```
cp  ~ghoffman/course_files/it244_files/five_lines.txt  .
```
Make sure the copy operation worked
```
ls
```
Run the program repeat.sh
```
./repeat.sh
```
Enter 5 lines of text when prompted by the script.

This program simply prints whatever input it receives to standard output.
Look at the contents of five_lines.txt
```
cat five_lines.txt
```
Run the same program taking input from a file
```
./repeat.sh < five_lines.txt
```
repeat.sh took its input from the file five_lines.txt and printed each line on the screen.

Create a file containing information on those connected to pe15.cs.umb.edu
```
who > current_users.txt
```
Display the contents of the file you just created
```
cat current_users.txt
```
Create a file containing a listing of all the files in my home directory
```
ls ~ghoffman > gh_dir.txt
```
Display the contents of the file you just created
```
cat gh_dir.txt
```

Use echo to send a string to a file.
```
echo foo > lines.txt
```
Use cat to display the contents of lines.txt
```
cat lines.txt
```
Write another string to lines.txt
```
echo bar > lines.txt
```
Use cat to display the contents of lines.txt
```
cat lines.txt
```
Notice that the previous contents of lines.txt have vanished.
Send another line to lines.txt
```
echo bletch >> lines.txt
```
Use cat to display the contents of lines.txt
```
cat lines.txt
```
Notice that your first line is still there.
Send still another line to the file
```
echo bling >> lines.txt
```
Run cat on lines.txt
```
cat lines.txt
```

Use echo to display a string in your terminal session window
```
echo bonkers
```
Now perform the same operation, but send output to /dev/null
```
echo bonkers > /dev/null
```
Nothing appears in the terminal window since you have sent the string "bonkers" into oblivion by redirecting the output of echo to /dev/null.

Make sure you are in your ex12 directory
```
pwd
```
If not, see me.
Create the script ex12.sh
```
nano  ex12.sh
```
Write into this file the commands from certain sections above

Enter all commands from the section Redirecting output up to the and including the section /dev/null

Do not enter commands from the section Redirecting input
Save this file

Save and quit.
Make this file executable
```
chmod 755 ex12.sh
```
Run this script looking for error messages
```
bash  ex12.sh > /dev/null
```
Running ex12.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/ex12.sh
```
When the script asks if you are ready for more, hit Return or Enter.
Let me check your script