Bash - Compare User input with array

Question

I want to validate did user input proper device in whiptail dialog or did user input something wrong.

I'm googling this for 2 days and can'f find any similar question/issue.

This is my code:

ALL_DEVICES=$(ifconfig -a | grep Ethernet | awk '{print $1}' | tr '\n' ' ' | sed -e 's/[[:space:]]*$//')
U_INPUT=$(whiptail --title "[choose]" --inputbox "Please input your device" 0 0 all 3>&1 1>&2 2>&3)

If I do echo "$ALL_DEVICES" I'll get: eth0 wlan0

Let's assume that user input: eth wlan0 wlan1

How can I inform user that he input correctly: wlan0 , BUT eth and wlan1 is incorrect input, since that devices doesn't exist.

I tried this code:

ALL_DEVICES=$(ifconfig -a | grep Ethernet | awk '{print $1}' | tr '\n' ' ' | sed -e 's/[[:space:]]*$//')
U_INPUT=$(whiptail --title "[choose]" --inputbox "Please input your device" 0 0 3>&1 1>&2 2>&3)

arr1=("$ALL_DEVICES")
arr2=("$U_INPUT")

echo "arr1 ${arr1[@]}"
echo "arr2 ${arr2[@]}"

FOUND="echo ${arr1[*]} | grep ${arr2[*]}"

if [ "${FOUND}" != "" ]; then
   echo "Valid interfaces: ${arr2[*]}"
else
   echo "Invalid interfaces: ${arr2[*]}"
fi

Thank you very much

Answer 1

I would go like this:

devices="eth0 wlan0"
input="eth0 whlan0 wlan0"

#translate output strings to array based on space
IFS='  ' read -r -a devicesa <<< "$devices"
IFS='  ' read -r -a inputa <<< "$input"


for i in "${inputa[@]}"
do
    for j in "${devicesa[@]}"; do
    if [ ${i} == ${j} ]; then
        correct=1
        break
    else
        correct=0
    fi
    done
    if [ $correct = 1 ]; then
        echo "device $i is correct"
    else
        echo "device $i isnt correct"
    fi

done

Maybe it could be more simplified, but you can read the steps to do. First go through array of strings, find devices, than compare them with user imput with writing walue about finding it. Last step is to clarify whether the value was found or not.