Bash script: YES/NO prompt example

Interactive Bash scripts will often include a yes or no prompt in order to ask for user verification before proceeding with a set of instructions or canceling the procedure.

If a user answers yes to the prompt, the Bash script will typically proceed with its task, and if a user answers no, the script will either exit or move on to a different part of the script.

In this tutorial, you will see how to create a yes/no prompt in a Bash script on a Linux system. See some of our examples below to learn how a yes/no prompt works.

In this tutorial you will learn:

How to create a yes or no prompt in Bash
How to loop a yes or no prompt for invalid responses
How to check for lowercase or uppercase responses

An example of a yes or no prompt in a Bash script on Linux

Software Requirements and Linux Command Line Conventions
Category	Requirements, Conventions or Software Version Used
System	Any Linux distro
Software	Bash shell (installed by default)
Other	Privileged access to your Linux system as root or via the `sudo` command.
Conventions	# – requires given linux commands to be executed with root privileges either directly as a root user or by use of `sudo` command $ – requires given linux commands to be executed as a regular non-privileged user

Bash script: YES/NO prompt example

We will read input from the command line by using the read command in our Bash script. This is best coupled with a case statement that can check to see if the user entered yes or no or something else.
```
#!/bin/bash

read -p "Do you want to proceed? (yes/no) " yn

case $yn in 
	yes ) echo ok, we will proceed;;
	no ) echo exiting...;
		exit;;
	* ) echo invalid response;
		exit 1;;
esac

echo doing stuff...
```
In this script, the read command asks the user if they would like to proceed, and waits for input. The response from the user is stored in variable $yn. The case statement then determines if the user entered yes, no, or something else, and proceeds accordingly. Here are the results when we execute the script:
```
$ ./test.sh 
Do you want to proceed? (yes/no) yes
ok, we will proceed
doing stuff...

$ ./test.sh 
Do you want to proceed? (yes/no) no
exiting...

$ ./test.sh 
Do you want to proceed? (yes/no) fdsfdsf
invalid response
```
One problem with the script above is that if a user erroneously enters an invalid response, the script does not attempt to get a correct answer, and instead proceeds to exit. This is not a problem in some situations, but sometimes we may want to continually prompt the user for a valid yes or no response. In that case, we can simply wrap our yes/no prompt in a while loop.
```
#!/bin/bash

while true; do

read -p "Do you want to proceed? (yes/no) " yn

case $yn in 
	yes ) echo ok, we will proceed;
		break;;
	no ) echo exiting...;
		exit;;
	* ) echo invalid response;;
esac

done

echo doing stuff...
```
Note that it was also necessary to add a break to the yes clause of our case statement. This tells Bash to exit the while loop in case the user answer affirmatively. We also dropped the exit command from our invalid response clause. Here is what happens when we enter invalid responses now:
```
$ ./test.sh 
Do you want to proceed? (yes/no) aaa
invalid response
Do you want to proceed? (yes/no) bbb
invalid response
Do you want to proceed? (yes/no) yes
ok, we will proceed
doing stuff...
```

Rather than forcing our users to type out a full yes or no, it is much more conventional to allow a response of y or n on Linux systems. Furthermore, let’s make sure our response is not case sensitive, so either a capital or lowercase letter can be entered.

#!/bin/bash

while true; do

read -p "Do you want to proceed? (y/n) " yn

case $yn in 
	[yY] ) echo ok, we will proceed;
		break;;
	[nN] ) echo exiting...;
		exit;;
	* ) echo invalid response;;
esac

done

echo doing stuff...

View the result below. This is much more convenient for the user since they do not need to spell the word, and do not need to worry about if their caps lock is on or not.

$ ./test.sh 
Do you want to proceed? (y/n) Y
ok, we will proceed
doing stuff...

$ ./test.sh 
Do you want to proceed? (y/n) N
exiting...

$ ./test.sh
Do you want to proceed? (y/n) y
ok, we will proceed
doing stuff...

$ ./test.sh 
Do you want to proceed? (y/n) n
exiting...

Closing Thoughts

In this tutorial, we saw how to create a simple yes or no prompt in a Bash script on a Linux system. There are more ways this can be done, but the most common is a read command and a case statement inside of a while loop. It is also most common to ask for a one letter response rather than typing out a whole word, although you could easily adapt your script to accept either kind of answer.

Bash script: YES/NO prompt example

Closing Thoughts

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