setting environment variables from ENTRYPOINT

Dockerfile

FROM jpetazzo/busybox
ADD entrypoint.sh /
ENTRYPOINT ["/entrypoint.sh"]
CMD ["sh", "-c", "echo $SOME_TEST_VARIABLE"]

entrypoint.sh

#!/bin/sh
export SOME_TEST_VARIABLE='this is my test variable contents from the ENTRYPOINT'
exec "$@"

output.txt

this is my test variable contents from the ENTRYPOINT