while loop to check for user input not in for loop

Question

I am listing files from a folder and taking an input from the user to select one of the files.

files=$(ls ~/VideoExtract/*.avi)
i=1
for j in $files
do
echo "$i.$j"
file[i]=$j
i=$(( i + 1 ))
done
echo ""
echo ""
read -p "Enter the serial number from the above list : " input
clear

Suppose if I have 3 files, the above code lists all three files listed with serial numbers 1,2,3. I want to validate if the user provides the correct input and not break the code till receiving a correct input. To do this, I have used a while loop after the above code

while [[ "$input" =~ ["$i"] ]]
do
echo "Please provide a serial number from the list given below."
files=$(ls ~/VideoExtract/*.avi)
i=1
for j in $files
do
echo "$i.$j"
file[i]=$j
i=$(( i + 1 ))
done
read -p "Enter the serial number from the above list : " input
done

This does returns the list of files again. The problem is, if I have 3 files, and if I type 4, the loop continues to work, but if I provide 5 instead, the loop breaks and moves on to the next line of the code. I am not sure if the problem is in line

while [[ "$input" =~ ["$i"] ]] 

or

i=$(( i + 1 ))

Instead of =~ I have tried with != and ! $input == $i and similar other combinations, such as with and without [] for $i. Nothing seem to work.

How do I run the while loop till the time the user provides a valid input that is within the range of $i.

Answer 1

(On a mobile so a somewhat shorter than I'd prefer)

=~ is a Regular Expression match. You don't want this here. Use -lt (less than) or -le (less than or equal) instead.

There are also a number of other problems with your code

• don't use ls to list a set of files, just use the set of files directly files=(~/VideoExtract/*.avi)
• quote your variables when you use them file["$i"]="$j"
• let the shell control the expansion of $files when you iterate over it for j in "${files[@]}"
• not strictly necessary, but indenting your code blocks will make the code far far easier to read