Prompting for User Input in Bash Scripts: A Modern Approach

In many scenarios, interacting with users directly through the terminal is necessary to make scripts flexible and dynamic. Whether you’re building an installation script, a configuration utility, or simply want to confirm an action, prompting for user input is a common task. In this blog post, we’ll explore how to effectively prompt for a “Yes,” “No,” or “Cancel” response in a Bash script using contemporary techniques that enhance user experience and script robustness.

Basic Method: Using read

The read command is the simplest method to prompt for user input in a Bash script. Here’s a straightforward example:

#!/bin/bash

echo "Do you wish to continue with the installation?"
read -p "(Y)es, (N)o, or (C)ancel: " answer

case "$answer" in
    [Yy]* ) echo "Installation started...";;
    [Nn]* ) echo "Installation aborted."; exit;;
    [Cc]* ) echo "Operation canceled."; exit;;
    * ) echo "Invalid input";;
esac

This script prompts the user and uses a case statement to handle the response appropriately. The use of wildcards (*) in the case statement allows any response starting with “Y” or “y” (and similarly for “N” and “C”) to trigger the corresponding block of code.

Improved User Experience with Default Choices

To improve user experience, especially in scripts where a default choice is often preferred, you can set a timeout and default option using read's -t (timeout) and -i (input prefill) options:

#!/bin/bash

read -p "Do you wish to continue with the installation? (Y/n/c) " -t 10 -i Y -n 1 answer
echo # Move to a new line
case "$answer" in
    [Yy]* ) echo "Installation started...";;
    [Nn]* ) echo "Installation aborted."; exit;;
    [Cc]* ) echo "Operation canceled."; exit;;
    * ) echo "Defaulting to Yes"; echo "Installation started...";;
esac

This version of the script makes “Yes” the default choice and continues the installation if no input is provided within 10 seconds, enhancing the automation capabilities of the script.

Handling Input without New Line Characters

For scripts where you don’t want the user to press the Enter key, you can use stty to change terminal settings temporarily:

#!/bin/bash

echo "Do you wish to continue with the installation? (Y/n/c)"
old_stty_cfg=$(stty -g)
stty raw -echo
answer=$(head -c 1)
stty "$old_stty_cfg"

echo # New line
case "$answer" in
    [Yy] ) echo "Installation started...";;
    [Nn] ) echo "Installation aborted."; exit;;
    [Cc] ) echo "Operation canceled."; exit;;
    * ) echo "Invalid input";;
esac

This script changes the terminal mode to raw and turns off echo, allowing it to read a single character without waiting for Enter. It then restores the previous terminal settings.

Prompting for user input in Bash scripts is not only about capturing user preferences but also about enhancing the interactivity and usability of your scripts. By using modern Bash features like timeout and default inputs or modifying terminal behavior for single-character inputs, you can make your scripts more user-friendly and efficient. Whether for simple confirmations or more complex user interactions, these techniques provide a solid foundation for building robust and interactive Bash scripts.