While循环测试bash脚本中是否存在文件

Question

I am trying to create a loop to prompt the user to create a file. If the file already exists, it will keep prompting the user until the user enters a file that does not exist. But can't seem to get it to work, anyone can help, please?

file3=/root/simulate/$filename
while true ; do
    if [ ! -f "$file3" ]; then
        read -p "Please enter a file name to create in simulate folder:" filename
        touch /root/simulate/$filename
    elif [ -f "$file3" ]; then
        read -p "Please enter a different file name as $filename already exist:" filename
        touch /root/simulate/$filename
        break
    else
        touch /root/simulate/$filename
    fi
done        

Answer 1

filename variable is empty.

There are two way to fill in filename variable

1. filename variable can pass on shell script by export command. ex) $export filename=newFile if you execute shell script, shell is forking and execute new shell. new shell taken your mother shell's Environment variables

2. Push filename variable into shell script.

note: I picked second way and I changed path of $file3.

I fixed codes in block of elif to ask again if something goes wrong.

this is a code.

#!/bin/bash
filename=newFile
file3="./$filename"

while true ; do
    if [ ! -f "$file3" ]; then
        read -p "Please enter a file name to create in simulate folder:" filename
        touch ./$filename
        break
    elif [ -f "$file3" ]; then
        while true ; do
            read -p "Please enter a different file name as $filename already exist:" filename

            if [ ! -f "$filename" ]; then
                touch ./$filename
                break 2
            fi
        done
    else
        touch ./$filename
    fi
done