echo "Bash" > intro

Learning outcomes

  • You will Learn basic and more advanced commands
  • You will be able to Write basic scripts
  • You will know how to Debug them
  • You will be able to Improve your work productivity

Examples

  • search for a sequence of characters inside several files
  • start a webserver locally
  • get information on your network
  • ...

Plan

  1. Basic introduction: Set up your environment, few commands to warm up a bit. Users, authorization...
  2. Your first script
  3. More advanced commands (grep, awk, sed...) & Introduction to regular expression
  4. Process & system management
  5. Final Hands-on

YouR environment (MAC/Linux)

YouR environment (MAC only)

# issamhammi at issams-air.home in ~ [18:09:27]
→ bash --version
GNU bash, version 5.0.18(1)-release (x86_64-apple-darwin19.5.0)
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

https://itnext.io/upgrading-bash-on-macos-7138bd1066ba

YouR environment (Windows)

A bit of theory

Bourne Again SHell or commonly called Bash is a command language interpreter

A bit of theory

A Shell is a program taking commands from the keyboard ans passing them to the operating system to be executed. Today shells are accessible through terminals

A script allows a set of commands to be executed one after the other

A bit of theory

A bit of theory

A bit of theory

Enough with that SH*T, I want to Code !

Basic Commands

  • cd - change directory
  • pwd - print working directory
  • ls - list content
  • cat - concatenate files and print output
  • touch - create a file
  • echo - display a line of text
  • mkdir - make a directory
  • rm - remove a file or directory
  • mv - move a file or directory

Basic Commands - practice

  1. make a directory called pokemon
  2. change directory to the pokemon folder
  3. create a file called pikachu.txt
  4. change the name of pikachu.txt to evee.txt
  5. make a copy of the evee.txt file and call it evee2.txt
  6. remove the evee2.txt file
  7. make a copy of the first folder and call it pokemon2
  8. remove the pokemon2 folder

Basic Commands - practice

  1. What does the man command do? Type in man rm. How do you scroll and get out?
  2. Look at the man page for ls. What does the -l flag do? What does the -a flag do?
  3. Type the following command to download and save the contents of google.com: curl https://www.google.com > google.html
  4. Use less to look at the contents of google.html.
  5. Look at the man page for less. Read the section on /pattern. Search for the text hplogo in the google.html file.

Basic Commands - practice

  1. How do you jump between words in the terminal?
  2. How do you get to the end of a line in terminal?
  3. How do you move your cursor to the beginning in terminal?
  4. How do you delete a word (without pressing backspace multiple times) in terminal?
  5. What is the difference between a terminal and shell?
  6. What is an absolute path?
  7. What is an relative path?
  8. What is a flag? Give three examples of flags you have used.
  9. What do the r and f flags do with the rm command?

Linux filesystem

path
/bin where I can find my binaries (ls, cat...)
/sbin system administrator binaries (used by root)
/boot where lives your OS (do not touch)
/etc etcetera - system config files
/dev special folder dedicated to hardware
/lib libraries required by the binaries to run
/sys kernel system files (do not touch)
/var files expecting to grow in files (logs)
/root root user dedicated folder
/usr installed user applications
/home user files

Quiz

  1. Where are my personal programs located ?
  2. What does etc stands for ?
  3. Should I touch the files in /boot if I am new to Linux ?
  4. As a standard user, will I be able to see what is inside antother /home directory ?
  5. Is Linux a file system operating system ?

Environment Variables

Variables accessible outside of your program.

  • printenv or set -> list your environment variables
  • echo $BASH_VERSION -> print your bash version
  • export POKEMON=pikachu -> set a new env variable

Environment Variables

$SHELL

$HOME

$PATH

...

.BASHRC file

When a login shell is started, it reads and execute commands from this file.

Users and groups

Users and groups

chmod u=rwx,g=rx,o=r myfile
chmod 754 myfile
chmod +x myfile

Permissions

Permissions

Number Permission rwx (display in terminal)
0 none ---
1 execute --x
2 write only -w-
3 write and execute -wx
4 read only r--
5 read and execute r-x
6 read and write rw-
7 read, write and execute rwx

Permissions

  • adduser -> add a new user
  • addgroup -> create a new group
  • chmod -> manage and change permissions
  • su -> switch to user
  • chown/chgrp -> manage and change owner and groups
  • sudo -> gives the power of the root user

PRACTICE

  1. Create a file called restricted.txt.
  2. Change the permissions on the restricted.txt file to allow the owner to read and write to the restricted.txt file.
  3. Change the permissions on the restricted.txt file to only allow the owner, group and everyone to read and write and execute the restricted.txt file.
  4. Create a folder called secret_files. Inside the secret_files folder create a file called first_secret.txt and another folder called classified. Inside of the classified folder create a file called super_secret.txt.
  5. Change the permissions on the secret_files to only allow the owner and group to read, write and execute in all the files and folders inside of secret_files.
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