Docker - call command from entrypoint.sh

Dockerfile

FROM alpine

COPY entrypoint.sh /
RUN chmod +x /entrypoint.sh
ENTRYPOINT [ "/entrypoint.sh" ]
CMD echo 'hello, captain!'
ENV FOO=bar

entrypoint.sh

#!/bin/sh

# exit on first error (opposite of default shell behavior)
set -e

# print executed commands. Useful for debugging. Be careful to not expose secrets!
# set -x

# perform some work and access the env variables that are defined by docker
echo "$FOO"

# the CMD is accessbile via $@
# you can just execute it:
#
# exec $@
#
# or use it like a real docker entrypoint
# i.e.

printenv | grep $@

example

$ docker build -t test .
$ docker run test foo
bar