command_line_exercises.md

Introduction to the Unix Command Line: Exercises

Obtaining the sample data:

git clone https://github.com/callaghanmt/shell-training.git

###Exercise 1

Create the following directory tree in your home directory (~):

work
work/input_data/
work/results/
work/program/

Create the file input.txtwith a text editor and put some text in it.

Move the file to work/input_data and rename it in the same command to control01.txt

Create this directory tree in one line only: work/experiment/results/report

Delete the work directory and all of its contents with one single command.

###Exercise 2

Two new commands:

• The sort command will sort lines alphabetically
• You can use the cut command to split lines of text based on a given character e.g. cut -d ',' -f 2 will split lines around the comma and give you the second part

Combine cat, cut, and sort to print out the Latin names from birds.txt in alphabetical order

Save the output to a new file

###Exercise 3

List all the animals on the Isle of Man alphabetically and find the 50th item in that list

###Exercise 4

shell-training/data/ contains 300 data files, each of which should contain 100 values. One of these files is missing some data though...

Use a series of commands connected by pipes to identify the file with missing data

hint wc -w will tell you the number of values in a file, sort -n will sort numerically

###Exercise 5

• In the wildcards directory, create a variable called files listing all of the text files.
• Loop through this list and print out the first line from each file.

###Exercise 6

What will this command print to the screen?

[user@host wildcards]$ for filename in *.txt
> do
> echo $filename
> cat $filename > new-file.txt
> done

What will the contents of new-file.txt be and why?

###Exercise 7

Recreate the a_directory/inside/the_other tree if you deleted it.

Add write permission for users from your group for the full directory tree with one single chmod command (look in the man pages for more information).

What happens if you can read but not execute a directory?

###Exercise 8

Create a "Hello world"-like script using a text editor and execute it.

Redirect the output from your script to a file or another program.

###Exercise 9

Write a script which will create as many numbered directories as you want when you run it.

###Exercise 10

Write your own mid command which will print a selection of lines from the middle of a file depending on the arguments you pass to it.