Create dynamic variable name bash and get value - bash

Question

I have a function in bash that get param a string, for example:
MYSQL_DATABASE then I want in my file to create a var named VAR_MYSQL_DATABASE but I can`t get the value.
create_var()
{
read -p "Enter $1 : " VAR_$1
printf VAR_$1 // print VAR_MYSQL_DATABASE_NAME instead what I typed, so how do I get the value?
if [[ -z VAR_$1 ]]; then
printf '%s\n' "No input entered. Enter $1"
create_entry $1
fi
}
create_var "MYSQL_DATABASE_NAME"

Answer 1

Use the declare built-in in bash,
name="MYSQL_DATABASE"
declare VAR_${name}="Some junk string"
printf "%s\n" "${VAR_MYSQL_DATABASE}"
Some junk string
With the above logic, you can modify how your name variable is controlled, either present locally. If it is passed as argument from a function/command-line do
declare VAR_${1}="Your string value here"
Perhaps you want to achieve something like this,
create_var()
{
read -p "Enter value: " value
declare -g VAR_$1="$value"
dynamVar="VAR_$1"
if [[ -z "${!dynamVar}" ]]; then
printf '%s\n' "No input entered. Enter $1"
create_entry $1
fi
}
So, here we are creating the dynamic variable using the declare built-in and with the dynamic part VAR_$1 cannot be referenced directly as normal variables, hence using indirect expansion {!variable} to see if the created variable is available.

Answer 2

Try the following :
#!/bin/bash
create_var() {
declare -g VAR_$1
ref=VAR_$1
read -p "Enter $1: " "VAR_$1"
echo "inside : ${!ref}"
}
create_var "MYSQL_DATABASE_NAME"
echo "output : $VAR_MYSQL_DATABASE_NAME"
declare -g will make sure the variable exists outside of the function scope, and "VAR_$1" is used to dynamically create the variable names.
Output :
Enter MYSQL_DATABASE_NAME: Apple
inside : Apple
output : Apple

Answer 3

You can use the printf function with the -v option to "print" to a variable name.
create_var()
{
while : ; do
IFS= read -r -p "Enter $1 : " value
if [[ -n $value ]]; then
printf -v "VAR_$1" '%s' "$value"
return
fi
printf 'No input entered. Enter %s\n' "$1"
done
}
(I've rewritten your function with a loop to avoid what appeared to be an attempt at recursion.)