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JSI Tip 1005. How can I test if an environment variable exists?

If you need to test for the existance of an environment variable, you might consider using:

if not "%var%"

"" @echo var=%var%

While this works, a better method is:

if defined var @echo var=%var%

Try this little test:

@echo off
if not "%var%""" @echo line 3 %var%
if defined var @echo line 4 %var%
set var=hello world
if not "%var%"=="" @echo line 6 %var%
if defined var @echo line 7 %var%

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