Making GUIs in terminal using whiptail

Bharat Kalluri / 2021-01-20

Why

I have a bash script which installs all the software I use. I try out different linux distributions all the time, and it helps to optimize the setup piece for each fresh install.

I've had a script which asks a bunch of questions, each question is mapped to a function.If answered with yes executes that corresponding function. If answered with no, skips the function and will ask if the next function should be executed. An example of a function would be setup_zsh. If yes, it will install zsh and its plugins. Else, it will be skipped.

This works fine, but a neat improvement would be if there was a GUI where I can select options from a check list. And based on the selection, execute the corresponding functions. This is what got me looking into whiptail. Whiptail is a part of a package called newt. This is pre-installed in debian derivative(ubuntu, elementary OS etc..), but for some reason not pre installed in fedora.

How

Whiptail's commands are pretty straightforward. To make a message box, all you have to do is

whiptail --msgbox --title "Message Box example" "This is an example of a message box" 20 78

I think it is pretty readable, the first argument is the type, second is the title flag with the title which needs to be specified, third is the message and the fourth and fifth are the height and the width.

Similarly, a yes/no message box would be

if (whiptail --yesno "Yes or no demo" 20 78); then echo "yes";fi

A radio list

sampleOptions=("one" "two")
entries=()
for o in $sampleOptions;do entries+=("$o" "$o" "OFF");done
entriesLength=${#entries[@]}
radioDemoResponse=$(whiptail --radiolist --title "Radio List" "Demo of a radio list" 20 78 $entriesLength --
"${entries[@]}" 3>&1 1>&2 2>&3)
echo $radioDemoResponse

This one is slightly more complicated, The idea is that whiptail expects two important parameters after the usual. length of the enties and the entries themselves. The entires must be structured in (<value> <message> <state>). So if two radio buttons are needed, we will be having 6 entries.

In line one, we setup the array. In line two, an empty array is declared, later on the entires array is populated with data as whiptail expects it. The fourth line stores the length of the array up until this point. Pay attention to the # up front, that will tell bash that we are looking for the length of the array. the @ symbol tells that it should include the entire array. Later on we just setup whiptail with the parameters and retrieve the response. There is a -- before the entries so that whiptail does not mis understand that the array is not program parameters. To understand more about bash arrays, I suggest referring to this article.

The 3>&1 1>&2 2>&3 talks about data redirection, this topic is too big to cover in this post. I will be doing another post talking about redirection.

A Check box list

sampleOptions=("one" "two")
entries=()
for o in $sampleOptions;do entries+=("$o" "$o" "OFF");done
entriesLength=${#entries[@]}
radioDemoResponse=$(whiptail --checklist --title "Radio List" "Demo of a radio list" 20 78 $entriesLength --
"${entries[@]}" 3>&1 1>&2 2>&3)
echo $radioDemoResponse

This is exactly similar to the previous example, only the widget type changes from radiolist to checklist.

Now that we have the toolbox ready, let us dive into the actual implementation.

# Whiptail UI
STEP_LIST=(
'install_fonts' 'Install fonts'
'setup_ubuntu' 'Update and setup ubuntu'
'setup_macos' 'Update and setup macOS'
'setup_pi' 'Update and setup raspberry pi'
'setup_fedora' 'Update and setup fedora'
'setup_oh_my_zsh' 'Install oh my ZSH!'
'setup_git' 'Setup git email and name'
'setup_node' 'Install node using NVM'
'setup_rust' 'Install Rust'
'setup_docker' 'Install docker'
'setup_flutter' 'Install flutter and its toolchain'
'setup_miniconda' 'Setup python using miniconda'
'setup_albert' 'Install albert plugins'
'setup_fzf' 'Setup FZF'
'setup_ssh_keys' 'Create and setup ssh keys'
)
entry_options=()
entries_count=${#STEP_LIST[@]}
message='Choose the steps to run!'
for i in ${!STEP_LIST[@]}; do
if [ $((i % 2)) == 0 ]; then
entry_options+=($(($i / 2)))
entry_options+=("${STEP_LIST[$(($i + 1))]}")
entry_options+=('OFF')
fi
done
SELECTED_STEPS_RAW=$(
whiptail \
--checklist \
--separate-output \
--title 'Setup' \
"$message" \
40 50 \
"$entries_count" -- "${entry_options[@]}" \
3>&1 1>&2 2>&3
)
if [[ ! -z SELECTED_STEPS_RAW ]]; then
for STEP_FN_ID in ${SELECTED_STEPS_RAW[@]}; do
FN_NAME_ID=$(($STEP_FN_ID * 2))
STEP_FN_NAME="${STEP_LIST[$FN_NAME_ID]}"
echo "---Running ${STEP_FN_NAME}---"
$STEP_FN_NAME
done
fi

Since context has been already set-up, this should be straightforward. Since I personally use this, I wanted the messages to be clear. So every even element has the function name and every odd element has its description(I know I could have used associative arrays, but for now this is good enough since this is a personal script).

The setup is completely the same as check list example, just that the array population happens with <fn_name> <message> OFF. I also divide the index by two so that I get the right numbering, instead of 0, 2, 4 I get 0, 1, 2. After whiptail finishes the UI and returns the result, the result is iterated on. Every ID is multiplied by two (since we divided it earlier) and the corresponding function is executed.

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