Creating a string variable name from the value of another string

Question

In my bash script I have two variables CONFIG_OPTION and CONFIG_VALUE which contain string VENDOR_NAME and Default_Vendor

Answer 1

This uses bash builtins:

#!/bin/bash

VAR1="VAR2"

declare "${VAR1}"="value"

echo "VAR1=${VAR1}"
echo "VAR2=${VAR2}"

The script output:

VAR1=VAR2
VAR2=value

Here's the snippet using your variable names:

#!/bin/bash

CONFIG_OPTION="VENDOR_NAME"

declare "${CONFIG_OPTION}"="value"

echo "CONFIG_OPTION=${CONFIG_OPTION}"
echo "VENDOR_NAME=${VENDOR_NAME}"

The script output:

CONFIG_OPTION=VENDOR_NAME
VENDOR_NAME=value

Answer 2

I know that nobody will mention it, so here I go. You can use printf!

#!/bin/bash

CONFIG_OPTION="VENDOR_NAME"
CONFIG_VALUE="Default_Vendor"

printf -v "$CONFIG_OPTION" "%s" "$CONFIG_VALUE"

# Don't believe me?
echo "$VENDOR_NAME"

Answer 3

For pure shell, possibly try:

#!/usr/bin/env sh

option=vendor_name
value="my vendor"

eval $option="'$value'" # be careful with ', \n, and \ in value
eval echo "\$$option" # my vendor
echo "$vendor_name" # my vendor

Why?

#!/usr/bin/env sh
printf -v "var" "val" # prints the flag, var not set
declare var=val # sh: declare: not found
echo ${!var} # sh: syntax error: bad substitution

I don't like eval, but are there any POSIX options?