How do I prompt for Yes/No/Cancel input in a Linux shell script?

Question

I want to pause input in a shell script, and prompt the user for choices.
The standard Yes, No, or Cancel type question.
How do I accomplish this in a typical bash prompt?

Answer 1

The simplest and most widely available method to get user input at a shell prompt is the read command. The best way to illustrate its use is a simple demonstration:

while true; do     read -p "Do you wish to install this program? " yn     case $yn in         [Yy]* ) make install; break;;         [Nn]* ) exit;;         * ) echo "Please answer yes or no.";;     esac done 

Another method, pointed out by Steven Huwig, is Bash's select command. Here is the same example using select:

echo "Do you wish to install this program?" select yn in "Yes" "No"; do     case $yn in         Yes ) make install; break;;         No ) exit;;     esac done 

With select you don't need to sanitize the input – it displays the available choices, and you type a number corresponding to your choice. It also loops automatically, so there's no need for a while true loop to retry if they give invalid input.

Also, Léa Gris demonstrated a way to make the request language agnostic in her answer. Adapting my first example to better serve multiple languages might look like this:

set -- $(locale LC_MESSAGES) yesptrn="$1"; noptrn="$2"; yesword="$3"; noword="$4"  while true; do     read -p "Install (${yesword} / ${noword})? " yn     if [[ "$yn" =~ $yesexpr ]]; then make install; exit; fi     if [[ "$yn" =~ $noexpr ]]; then exit; fi     echo "Answer ${yesword} / ${noword}." done 

Obviously other communication strings remain untranslated here (Install, Answer) which would need to be addressed in a more fully completed translation, but even a partial translation would be helpful in many cases.

Finally, please check out the excellent answer by F. Hauri.