28. Variables and Input/Output in Bash

Scripts become powerful when they can store information (variables) and interact with the user (input/output).

1. Defining and Using Variables

In Bash, variables are defined using the NAME=VALUE syntax (no spaces around the equals sign!). To access the value, use a dollar sign ($).

bash #!/bin/bash

GREETING="Hello, Bash user" HOST=$(uname -n) # Command substitution to capture output

echo "$GREETING on device $HOST"

Note on Quoting: Always use double quotes (") when referencing variables, especially if they contain spaces, to prevent word splitting.

We have used echo extensively. It simply prints text or variable contents to the standard output.

The read command prompts the user and stores their input into a specified variable.

bash #!/bin/bash

echo "Please enter your project name:" read PROJECT_NAME

echo "Creating project folder: $PROJECT_NAME" mkdir $PROJECT_NAME

Improved Input: You can combine the prompt and input using the -p (prompt) flag with read:

bash read -p "Enter desired filename: " FILENAME touch $FILENAME