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Shell Scripting: Linux Command Line Automation Guide

The clearest way to speed up repetitive tasks in the Linux terminal is to use shell scripts.
In this guide, you will write a script from scratch, run it and make it interactive.

What Will You Learn in This Guide?​

  • What is shell script and why is it used?
  • .sh file creation and shebang logic
  • Script execution and permission management
  • Variables and receiving input from the user
  • Practical tips for error checking

What is Shell Script?​

Shell script is an automation file in which Linux commands are written sequentially.
The aim is to run manual jobs with a single command.

1. Getting Started with Shebang​

Each shell script must specify which interpreter to use.
This line is called shebang.

#!/bin/bash
  • This line tells the script to run in Bash.

Alternatively:


#!/bin/sh
  • This line uses the generic shell interpreter.

2. Creating the First Shell Script File​

  1. Create a new file with a text editor.

vi ilk_betik.sh
  • This command opens a new script file.

Add the following to the file:


#!/bin/bash
  • Shows active user and date
date
  • This script prints the username and system date to the screen.

3. Script Execution Methods​

  • You can run the script in two ways.
  1. Running with Bash

bash ilk_betik.sh
  • This method does not require additional permissions.
  1. Direct operation

./ilk_betik.sh
  • This method requires execution permission.

4. Grant Run Permission (chmod)​

  • Add execute permission to the script.

chmod +x ilk_betik.sh
  • This command makes the file executable.

5. Variable Usage​

  1. In shell scripts, variables are defined without spaces.

#!/bin/bash

MESAJ="Merhaba Linux"
echo $MESAJ
  • This script prints the variable contents to the screen.

6. Getting Input from the User​

  1. It is possible to make scripts interactive.

#!/bin/bash

echo "Adınız nedir?"
read ISIM
echo "Merhaba $ISIM, hoş geldin"
  • This script takes the name from the user and generates a response.

7. Stopping the Script in Case of Error​

  1. When the command gives an error, you can ask the script to stop.

#!/bin/bash
set -e
  • This line stops the script when an error occurs.

Frequently Asked Questions (FAQ)​

1. Why does the script give a Permission denied error? There is no execution permission in the file. It is solved with chmod +x.

2. Why doesn't the script written in Windows work in Linux? Line endings are different. It must be converted with dos2unix.

3. Should I use sh instead of bash? For simple tasks, sh is sufficient. Bash is recommended for advanced scripts.

Result​

Shell scripts are the basis of automation in Linux systems. You can start with small scripts and build powerful workflows.

You can immediately run the scripts you create on high-performance servers on GenixNode infrastructure 🚀