Using read to Collect Keyboard Input

Many scripts run unattended, but interactive scripts ask questions and respond to what the user types. In Unix shell scripting, the read command is the standard way to collect keyboard input and store it in a variable so your script can make decisions or take actions based on that input.

In this lesson you will:

• prompt the user for input
• store the response in a variable
• print the value back to the screen as verification

Two variable rules you will use immediately:

1. You can name variables anything you want. Use descriptive names (for example MYNAME, RESPONSE, or DOWNLOADFILE).
2. To use the value stored in a variable, prefix the name with $ (for example $MYNAME).

The simplest form of read takes one parameter: the variable name that should receive the user’s input. A common pattern is:

echo "Enter the name of the file to download:"
read DOWNLOADFILE

When the script runs, the user sees the prompt and the cursor waits for input. After the user presses Enter, the text they typed is stored in DOWNLOADFILE.

Once you have captured input, you can use it anywhere in your script. A simple verification step is to print the value back to the user. For predictable formatting, printf is a strong choice:

printf "The name of the file you entered was: %s\n" "$DOWNLOADFILE"

Example output:

The name of the file you entered was: cruise_update.html

From here, scripts typically validate the input (for example, check if a file exists) before using it.

Different shells support different options. The following practices are widely useful:

• Use read -r when possible: this prevents backslashes from being treated as escape characters.
• Always quote variables: use "$VAR" to avoid bugs with spaces or special characters.
• Validate input: check for empty values and confirm files exist before acting on user input.

Example: prompt, read safely, and reject empty input:

echo "Enter a filename:"
read -r DOWNLOADFILE

if [ -z "$DOWNLOADFILE" ]; then
  echo "ERROR: You must enter a filename." 1>&2
  exit 1
fi

If you are specifically using bash, you may also see:

• read -p "Prompt: " VAR to print the prompt without a separate echo
• read -s VAR to read input silently (useful for passwords)
• read -t 10 VAR to time out after 10 seconds

The following sequence demonstrates a complete interactive input flow:

1. Start a Bourne shell (optional): sh
2. Print the prompt: echo "Please enter your name:"
3. Read a line of text into a variable: read -r MYNAME
4. Type your name and press Enter
5. Print a confirmation message using the variable: printf "Thank you, %s\n" "$MYNAME"

Later lessons expand this idea by using read inside loops to process files line-by-line and by combining input with conditional tests.

Click on the Exercise link below to practice what you have learned in the UNIX Lab.
Read keyboard Input command - Exercise
The next lesson shows you how to prepare a script file for execution.