This tutorial makes you familiar with bash, the Linux command line. You will learn to:

• navigate directories
• manipulate files
• execute programs

If you have no previous experience with Unix-like systems or know a few commands but would like to know more, this tutorial is for you.

Prerequisites

This tutorial was prepared for Ubuntu Linux, but it works on MacOS, Cygwin and the Git bash as well, given that Python 3 is installed on your system.

Goal

In this tutorial, you will be looking for a sentence containing 17 characters.

Solution:

All characters are hidden in the exercises below.

Preparations

• clone the repository using git
• locate the exercises/ folder
• open a bash terminal

1. Directories and files

1.1. Navigating directories

The first character is hidden in a file somewhere in the exercise1 directory tree. Use the commands

(do not type the pointy brackets, just insert the directory name) and

to move from one directory to the next. Look through subdirectories until you find one with the name solution_1.1 and list its contents. If you went to a wrong directory, you can go back one level by typing:

or go back to your home folder:

you can also use the ~ character to refer to you home directory:

Additionaly, you can print the absolute path of your current directory using

1.2. Show a hidden file

Some files are not visible immediately. To see them, you need the command

The second character, is in the same directory as the first one, but in a hidden file.

1.3. Execute a bash script

Use cd .. to go back to the directory exercise_1/directoryB/. To find the third character, you need to execute the bash script. On bash, this is done by typing 'source' and the name of the program:

You can run a bash script by using the ./ operator

What? It does not work? You can use the ./ operator only on executable files! Add executable permisions to program.sh, then run it using ./

+x means "add executable permissions".

Did you know? You can run multiple commands sequentially using the ; operator

chmod +x program.sh ; ./program.sh

1.4. Find out how big a file is

Go to the folder exercise_1/directoryC/. To find the fourth character, you need to find out how big the text file in the directory is. This is done with the command

In the table the command produces, you will find the file size in bytes, the file’s owner, permissions to read and modify it, and the date/time of the last modification.

To obtain the fourth character look up the file size in the Table of printable ASCII characters:

ASCII Table, Public Domain

When typing names of directories or files, press [TAB] after the first few characters. Unix tries to guess what you are typing.

1.5. Creating files

Did you know? You can use the 'touch' command to update the modification time of files. If the file you are touching does not exists, 'touch' will create it. The following commands creates the file new_file.txt Run the following command to observe the effect of touch:

2. Edit text files

Please use cd .. to go back to the top directory of the tutorial material. Then, change to the directory exercise_2.

2.1. See the content of a text file

In the directory exercise_2/, you will find a text file solution_2.1.txt. The fifth character is inside that file. To see its contents, use the command

You can also use the command 'less' to view the content of a file in a minimal text browser

Press 'q' to exit.

2.2. Edit text files and manual

You can edit files by opening a text editor such as VSCode or Vim. Fill text file with the characters you have found so far.

3. Copy and remove files

Please go to the directory exercise_3.

3.1. Create a directory and copy a file to it.

To find characters six, seven and eight, you need to create a subdirectory named solution in exercise_3/ and copy the files from the part1/ and part2/ folders into it.

For creating directories, use the command:

For copying, you can use the command

cp <filename from> <filename to>

Type ls -l solution/* afterwards to see the solution.

Did you know? Instead of copying, you can use the 'mv' command to move files and directories. The 'mv' command is especially useful to change the name of files or directories

mv <path to filename> <new path to new filename>

Use the command to move the directory 'solution' to you home, change the name of the directory to 'toBeRemoved'

3.2. Removing files

In the data directory, all files with an Y need to be deleted. To do so, use the command:

Also, there are more files to be deleted in the data directory. To remove more than one file at once, you can use * as a wildcard, i.e. rm ju* will delete all of junk.txt, juniper.txt and june.docx.

To get characters nine and ten, look at the files that remain after deleting all that contain a Y.

4. Process text data

Please go to the directory exercise_4.

4.1. comparing two files

There are two different versions of a quote, ai.txt, and artificial_intelligence.txt. To find out, how they differ, Unix provides the command

diff <filename1> <filename2>

The 11th character of the solution is the single character in which the two files differ.

4.2. Sorting a text file

Unix has a small program to sort text files alphabetically. It is called by

The symbol '|' is called a pipe and is often used to connect Unix programs to each other. In this case, the output of 'cat' is used as input for 'sort'. The 12th character of the solution is the first character of the last word in the alphabetically sorted file elephant.txt.

4.3. Redirecting output

You can use the '>' and '>>' to redirect the output of a command. For example, you can use '>' to redirect the output of 'echo' to file. 'echo' is a simple program that writes a string "<string>" to the standard output.

echo "new content" > outOfEcho.txt

Use 'cat' to see the content of outOfEcho.txt

Warning: If outOfEcho.txt does not exist, it will be created; furthermore, if outOfEcho.txt exists, its content will be erased!

You can use '>>' to append to the end of a file without erasing its content:

echo "new appended content" >> outOfEcho.txt

After running the previous two commands. The 13th character of the solution is the letter of the alphabet corresponding to the number of words in outOfEcho.txt

4.4. Finding words in a text file

To look for specific words in a text file, use the command

It produces all lines from the given file that contain the given word. The grep command is very powerful and can handle Regular Expressions.

To find the 14th character, search for the word fire in the file datascience.txt and take the first character of the output.

You can search through many files at once by including a * in the filename.

5. Command-line tools

The following can be done in any directory.

5.1. Check whether you have internet

The easiest way to check from the Unix command line whether the internet connection works, is to send a request to a known server (e.g. www.spiced-academy.com) using the command

The command reports, how long a message takes back and forth to the given server. To interrupt the messages, press Ctrl+C.

The 15th character is the ping option that sets the maximum number of requests to send before terminating the program. Check the documentation with:

5.2. Set an environment variable

To install some programs, it is necessary to set so-called environment variables. These can be set using the command

export <variable-name>=<value>

You can see all variables by the command

To obtain the 16th character, you need to use export to set the variable GIVEME to the value UNCHARACTERISTICALLY.

Find out the character position in the alphabet with:

Use the following command to understand the meaning of 'wc -c'

5.3. Managing processes

To see what programs are running on your machine, type

It displays you a list of all currently active programs. Shift+P sorts them by the CPU time they are using, Shift+M by the amount of memory they are using (if you don't see any program consuming lots of memory, start a web browser). Quit top by pressing q.

The last character of the solution is the first character of the first word in the line containing the column labels.

The 'kill' command sends a signal to the process with the specified <pid>. 9 specifies that you want to send a termination signal.

You find the pid number in the first column of the top output. Of course, you may only interrupt your own programs, not those owned by root, the system administrator.

You can also show the lists of processes using the 'ps' command:

The 'a' option means 'all'.

License

© 2010 Dr. Kristian Rother

This tutorial is published under the Creative Commons Attribution Share-alike License 4.0

Forked from https://github.com/krother/bash_tutorial.

Extended by Samuele Germiniani 2024.

Solution

APTENODYTES TEACUP