Tuto5: Bash scripting.md

Pracatical for Bash Scripting

+++ What is a Bash :

• A Bash stands for "short for Bourne Again SHell", is a command-line shell and scripting language commonly used in Unix and Linux environments to chain a few shell commands together in a file for ease of use.
• It provides a powerful interface for interacting with your operating system and automating tasks.

+++ How to write a bash script

It is crucial to know tha a bash script involves creating a text file containing a series of Bash commands and instructions. So here's a step-by-step guide on how to write a basic Bash script:

• First create a Directory called script under letsPractice; (pwd : ~/letsPractice/scripts).

• Step 1: Open a Text Editor;
  • Start by opening a text editor of your choice. You can use command-line editors like nano or graphical editors like Visual Studio Code, Sublime Text, or Notepad++ any text editor of your choice.
  • For this example, let's assume you're using a simple command-line editor like nano.

nano my_first_script.sh

• The .sh extension refers to the scripting language commands file that contains computer program to be run by Unix shell.

• Step 2: Write a Shebang Line;
  • The first line is often called the "shebang" line. It specifies the interpreter that should be used to execute the script.
  • For Bash, the shebang line is:

#!/bin/bash

• Step 3: Write your first Bash Command;
  • Echo is one of the basic Unix/Linux command in linux and most commonly used in shell scripts, it is used for displaying lines of text or string which are passed as arguments on the command line.

echo " If you don't practice you don't deserve to win"

• Step 4: Add Comments to your bash file;
  • To describe what your script does or to provide context for others users, you may add a non-excuted lines which serves to explain or to provide a documentation.
  • Comments starts with a " # " symbol.

# This is test comment

• Step 5: Save your Script (your file);

  • Hint : In nano, you can press Ctrl + O, then press Enter to confirm the file name and save it. To exit nano, press Ctrl + X.

• Step 6: Make your Script Executable

  • Note that until now you just created an usual file which contains sentences but still undefined as command to be executed. So before you can run the script, you need to make it executable.
  • Navigate to the directory where your script is located, then type;

ls -l

• Your output will seems like : -rw-rw-r-- 1 user1 users size Month day time filename

• Note that there is no execute option neither for owner, group or others. So to change the permission we will use the "chmod" command as follows;

chmod a+x my_first_script.sh

• Now type againe ls -l what do you notice ?

chmod a-x my_first_script.sh

chmod 777 my_first_script.sh

chmod 700 my_first_script.sh

chmod 327 my_first_script.sh

• Step 7: Run your script; There many method to run you script,
• First method :

bash my_first_script.sh

• The second method is :

./my_first_script.sh 

• Third method :

source my_first_script.sh 

• Step 8: Run your script elsewhere other than your original directory;
  • Temporary:

• First check your current working directory path.

pwd 

• Add the directoty to the PATH temporarily (only for the current session), you can use the following command:

export PATH=$PATH:/your/directory/path

• Now you may simply type your name script then it will be executed:

my_first_script

• Permanently

• If you want to make the change permanent, you need to add the export command to one of your shell's configuration files:

echo 'export PATH=$PATH:/your/directory/path' >> ~/.bashrc

• Then

source ~/.bashrc

• Now you can notice that th command " export PATH=$PATH:/your/directory/path " was appended to the last line in .barshrc file then it may be executed anywere.

• Try to change your directory or exit from the terminal then open it, then execute your script it should run properly.