Uppercase and lowercase conversion in Bash Scripting

Introduction

Changing text to uppercase or lowercase helps make data consistent and easier to read or compare.

You want to make user input case-insensitive.

You need to format filenames or text to a standard case.

You want to compare two strings without case differences.

You are preparing text data for reports or logs.

Syntax

Bash Scripting

variable=${variable^^}  # Convert to uppercase
variable=${variable,,}  # Convert to lowercase

Use ${variable^^} to convert all letters in the variable to uppercase.

Use ${variable,,} to convert all letters in the variable to lowercase.

Examples

Converts the string 'hello' to uppercase and prints 'HELLO'.

Bash Scripting

name="hello"
echo ${name^^}

Converts the string 'WORLD' to lowercase and prints 'world'.

Bash Scripting

name="WORLD"
echo ${name,,}

Shows both uppercase and lowercase conversions of 'Bash Scripting'.

Bash Scripting

text="Bash Scripting"
echo ${text^^}
echo ${text,,}

Sample Program

This script takes a string, converts it to uppercase and lowercase, then prints all versions.

Bash Scripting

#!/bin/bash

input="Hello Bash"

# Convert to uppercase
upper=${input^^}

# Convert to lowercase
lower=${input,,}

# Print results
echo "Original: $input"
echo "Uppercase: $upper"
echo "Lowercase: $lower"

Important Notes

This uppercase/lowercase conversion works only on letters; numbers and symbols stay the same.

Make sure your script uses bash version 4 or higher for this syntax to work.

You can convert only the first letter by using ${variable^} or ${variable,}.

Summary

Use ${variable^^} to convert all letters to uppercase.

Use ${variable,,} to convert all letters to lowercase.

This helps keep text consistent and easy to compare.