IT 244: Introduction to Linux/Unix

IT 244 Class Exercise 11
Class 11 Exercise

Perform a long listing of the web directory for this course
```
ls -l /home/ghoffman/html/it244_html
```
Use ls to see the directory contents in reverse order by date
```
ls -ltr /home/ghoffman/html/it244_html
```
Here you are combining the options indicating you want a long listing (l), ordered by date and time (t), in reverse order (r).
Use ls to see the access permissions on the it244_html directory
```
ls -ld /home/ghoffman/html/it244_html
```
Here you are combining the options indicating you want a long listing (l) of the directory itself (d), not its contents.

Use df to see the disk space available on pe15.cs.umb.edu
```
df
```
Notice two things.

First, the available space field is very hard to read.

Second, you are seeing disk partitions on more than one machine.

The various blade entries are different machines.

The single, logical, filesystem we see is composed of multiple physical disks and partitions.
Now use df with the -h option
```
df -h
```
The free disk space is now much easier to read.

Invoke the --help option for cat
```
cat --help
```
Look at the help for ls
```
ls --help
```
Notice that some help is very long.
Explore the --help option for cd
```
cd --help
```
cd does not respond to the --help option, or, for that matter, -h.

Run ls using only the name of the command
```
ls  ~ghoffman
```
Learn the location of the ls executable file
```
which ls
```
Run ls using an absolute pathname
```
/bin/ls  ~ghoffman
```
This has the same effect as typing the name of the command on the command line, which is also the name of the executable file for ls.

Go to the ex11 directory
```
cd ~/it244/ex/ex11
```
Make sure you are in your ex11 directory
```
pwd
```
Run the shell script hello.sh which is in my course_files/it244_files directory
```
~ghoffman/course_files/it244_files/hello.sh
```

Copy hello.sh to your current directory

cp ~ghoffman/course_files/it244_files/hello.sh .

Make sure the copy operation worked
```
ls
```
Try to run the program you just copied using just the name of the file
```
hello.sh
```
You get an error message.
Run the program by placing ./ in front of the file name
```
./hello.sh
```
Now the program runs.

Run ls with no options or arguments
```
ls
```
Examine the exit status returned by the last command
```
echo $?
```
Since ls ran without any problems, it returned an exit status of 0, indicating that all went well.
Now run ls on a file that doesn't exist
```
ls foobar
```
Examine the exit status returned by the last command
```
echo $?
```
Since ls failed, it returns a non-zero exit status.
See what this exit status means
```
ls --help | tail
```
Returning the value 2 means ls ran into a serious problem.

Go to your ex11 directory
```
cd ~/it244/ex/ex11
```
Create the script ex11.sh
```
nano  ex11.sh
```
Write into this file the commands you used above
Include Unix commands from the section Combining Options up to and including the section Exit Status.
Save this file

Save and quit.
Test your script
```
~ghoffman/it244_test/ex11.sh
```
When the script asks if you are ready for more, hit Return or Enter.