Bash Scripting

 Bash is a command-line interpreter or Unix Shell and it is widely used in GNU/Linux Operating System.  It is written by Brian Jhan Fox. It is used as a default login shell for most Linux distributions. Scripting is used to automate the execution of the tasks so that humans do not need to perform them individually. Bash scripting is a great way to automate different types of tasks in a system. Developers can avoid doing repetitive tasks using bash scripting. 

Bash scripting supports variables, conditional statements, and loops just like programming languages. Below are some of the applications of Bash Scripts – 


Applications of Bash Scripts:

  • Manipulating files
  • Executing routine tasks like Backup operation
  • Automation

The advantages of using Bash Scripts are given below –


Advantages of Bash Scripts:

  • It is simple.
  • It helps to avoid doing repetitive tasks
  • Easy to use
  • Frequently performed tasks can be automated
  • A sequence of commands can be run as a single command.

The disadvantages of the Bash Scripts are given below – 

Disadvantages of Bash Scripts:

  • Any mistake while writing can be costly.
  • A new process launched for almost every shell command executed
  • Slow execution speed 
  • Compatibility problems between different platforms

How to Write Bash Scripts?

To write a Bash Script we will follow the steps –

  • First, we will create a file with the .sh extension.
  • Next, we will write down the bash scripts within it
  • After that, we will provide execution permission to it.

To create and write a file with the .sh extension we can use gedit text editor. The command for it will be –

gedit scriptname.sh

The first line of our script file will be –

#!/bin/bash

This will tell, the system to use Bash for execution. Then we can write our own scripts.

Let’s write down just a simple script that will print some lines in the terminal. The code for it will be –

#!/bin/bash         

echo "Hello, GeeksforGeeks"

Now we will save the file and provide the execution permission to it. To do so use the following command –

chmod +x scriptname.sh

Next to execute the following script we will use the following command –

./scriptname.sh

Here is the terminal shell pictorial depiction after executing the above commands as follows:  

 

Here the script file name is gfg.sh.

Now we can also write more complicated commands using Bash Scripts. Here is an example below in which we are using a condition statement –

Example Script:

#!/bin/bash         
Age=17
if [ "$Age" -ge 18 ]; then
    echo "You can vote"
else
    echo "You cannot vote"    
fi

Output:

You cannot vote

Here is the terminal shell pictorial depiction after executing the above script as follows:  

 

In the above way, we can execute multiple Bash commands all at once.


Now Let’s look into the other important concepts here :



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