Bash by Example: User Input
How to read input from the user during script execution using the read built-in command, understanding various read options like -p for prompts and -s for silent password input, using -t for timeout to prevent indefinite blocking, reading multiple variables in one command, and implementing robust input validation patterns.
Code
#!/bin/bash
# Prompt for input
echo "What is your name?"
read name
echo "Hello, $name!"
# Prompt with a message on the same line ( -p )
read -p "Enter your age: " age
echo "You are $age years old."
# Read a password silently ( -s )
read -s -p "Enter password: " password
echo
echo "Password saved (length: ${#password})"Explanation
Interactive scripts often need to accept user input. The read command is the standard tool for this. By default, it reads a line from standard input and assigns it to the specified variable. If no variable is provided, the input is stored in the default variable $REPLY.
The read command has several useful flags to improve the user experience. The -p flag allows you to specify a prompt string directly, keeping the input cursor on the same line. The -s flag (silent mode) prevents the user's input from being echoed to the screen, which is essential for reading sensitive data like passwords.
You can also use the -t flag to set a timeout, ensuring the script doesn't hang indefinitely if the user is away. Reading multiple variables at once is also possible; read var1 var2 splits the input line by whitespace.
Code Breakdown
read name pauses the script and waits for the user to type text and press Enter. The text is stored in the variable $name.read -p combines the prompt echo and the read action. This is cleaner and keeps the cursor at the end of the prompt text.read -s turns off local echo, so characters aren't displayed as they are typed. This is standard for password inputs.${#password} calculates the length of the password string, demonstrating that the data was captured correctly despite being invisible.