Bash scripting is a powerful tool for automating tasks, processing data, and making decisions based on conditions. In this blog post, we’ll explore various Bash commands and scripting techniques, explaining their purposes and providing examples along the way.

1. Echo Command

The echo command is used to print text to the terminal. It can also display the values of variables.

echo $0 $1 $2 $3 $4 $5 $6 $7 $8 $9

In this example, $0 represents the script’s name, while $1 to $9 are command-line arguments passed to the script. When you run the script as ./ or ./ orion insist, you can see how these variables capture the script’s name and arguments.

2. Variables and Input

Variables in Bash can hold various types of data, including strings and numbers. Here’s an example of variable usage:

myvariable="hello world"
echo $myvariable

You can also read user input and store it in a variable:

read varname
echo "varname: " $varname

When you run the script and enter a value, it will be stored in the varname variable and displayed on the screen.

3. Arithmetic Expressions

Bash supports arithmetic operations. You can perform calculations using various methods:

Using let:

let a=5+4
echo "1: " $a

let "a=5+4"
echo "2: " $a

Using expr:

expr 2 + 3  # Outputs: 5

Using $((expression)):

echo $a

4. Conditional Statements

Conditional statements allow you to make decisions in your scripts. Here are some examples:

If Statements:

if [ "$1" -eq 5 ]; then
    echo "Input is equal to 5"
    echo "Input is not equal to 5"

Case Statements:

case "$3" in
        echo "Starting"
        echo "Stopping"
        echo "Unknown command"

5. Loops

Loops are used to execute a block of code repeatedly. Here are some common loop types:

While Loop:

while [ $counter -lt 10 ]; do
    echo $counter

For Loop (C-style):

for ((i = 0; i < 10; i++)); do
    echo $i

For Loop (Iterating Over a List):

for l in $(ls); do
    echo $l

For Loop (Using Ranges):

for value in {1..5}; do
    echo $value

Until Loop:

until [ $counter -gt 10 ]; do
    echo $counter

6. Functions

Functions allow you to organize your code into reusable blocks. Here’s how you define and use functions in Bash:

function my_function {
    echo "This is a function"


7. Centering Text in Terminal

Lastly, here’s a script that centers text in the terminal:

cols=$(tput cols)
rows=$(tput lines)
half_input_length=$((input_length / 2))
middle_row=$((rows / 2))
middle_col=$((cols / 2 - half_input_length))
tput clear
tput cup $middle_row $middle_col
tput bold
echo $@
tput sgr0
tput cup $(tput lines) 0

Run this script with your desired message to see how it centers the text in the terminal.

By mastering these Bash scripting concepts, you can automate tasks and create efficient, robust scripts for various purposes. Whether you’re managing files, processing data, or making decisions based on conditions, Bash scripting is a valuable skill to have in your toolkit.