Learn Bash Scripting

Bash is a Unix shell and command language

What is Bash?

Bash (Bourne Again SHell) is a command-line interpreter that executes commands from a terminal or a file. Bash scripts are plain text files that contain a series of commands to be executed sequentially. Bash scripting allows you to automate tasks in Unix-like systems by writing a series of commands in a script file.

Learning Bash

1. Creating a Bash Script

A bash script is simply a text file with executable commands. By convention, scripts have a .sh extension. A basic example of a bash script would look like:

#!/bin/bash
echo "Hello, world!"

  • The first line #!/bin/bash is called a shebang. It tells the system to use Bash to execute the script.

  • The second line is a the echo command, which prints text to the screen.

2. Saving and Running the Script

  1. Save the file with the .sh extension (example, hello.sh)

  2. Make it executable by modifying the files permissions

chmod +x hello.sh

  1. Run the script by calling

./hello.sh

or

sh hello.sh

Bash Script Basics

Variables

name="Chloe"
echo "Hello, $name"

  • Don’t use spaces around the = when assigning value to a variable

  • Use $ to reference the variable

User Input

read -p "Enter your name: " user_name
echo "Welcome, $user_name!"

Conditionals

if [ "$name" = "Chloe" ]; then
  echo "That's you!"
else
  echo "That's not me!"
fi

Loops

For loop:

for i in 1 2 3
do
  echo "Number $i"
done

While loop:

count=1
while [ $count -le 3 }
do
  echo "Count is $count"
  count=$((count +1))
done

Functions

greet() {
  echo "Hi, $1!"
}

greet "Chloe"

Best Practices

  • Use meaningful variable names.

  • Always quote your variables ("${var}") when calling them to prevent issues with spaces.

  • Include comments to explain your code:

# This is a comment

Quality of Life Improvements

The default editor in bash for most linux systems is nano. Vim/Vi is an editor that can be especially useful for editing programs like bash scripts. Generally speaking, Vim is a more intuitive text editor, and will likely save you time and sanity when editing text files. You can set your default editor to vim by calling export EDITOR=vim. Additionally, if you want to take things a step further, you can edit your commands with vim keybindings directly in the command line set -o vi and if you don’t like this change you can always revert back set -o emacs. Most .bashrc configs come with ll being an alias to "ls -l", but if it’s not already set, you can add this alias, or other aliases, to the .bashrc file alias ll="ls -l".

Challenge

BashBlaze: 7 Days of Bash Scripting

Resources