How to get value of environment variable from passed command line parameter

Question

I have to use/reference an environment variable value which will be passed as a command line argument. Something like below

set myvar=%1
echo Value of %myvar% is %%myvar%%

Here in %%myvar%% I want to reference the value of that environment varible

A typical call to this script will be

script.bat JAVA_HOME

Since it's environment variable, why it must be passed as a command line parameter in the first place? Why can't the script use environment variables directly? — Esa Jokinen, Mar 09 '15 at 10:00
@EsaJokinen I need to create some scripts which will test whether certain environment variables exists before I start some tasks. Like before working with Java I want a script to check whether JAVA_HOME, ANT_HOME, M2_HOME is already set. In another language I may need some other environmental variables checked. I want to create a utility script which will check any given variable and to use that utility in other scripts — Tushar Joshi, Mar 10 '15 at 11:35

score 3 · Accepted Answer · edited May 23 '17 at 12:41

You don't need the intermediate myvar variable. If you want it, then simply substitute %myvar% for %1 below.

You need two rounds of expansion.

Option 1 - CALL

@echo off
call echo %%%1%%

In the first parsing phase

In the CALL phase, %JAVA_HOME% expands to the value you are looking for.

Option 2 - Delayed Expansion

@echo off
setlocal enableDelayedExpansion
echo !%1!

The delayed expansion form is much easier to read

1 Answers1