# How to prevent field splitting when using ENV variables in Docker ENTRYPOINT


By default, variables will be split by space characters. This is not what you want if you have a message that contains spaces for example.

To prevent this, the variable may be surrounded by quotation marks. If you’re using the [exec form](https://docs.docker.com/engine/reference/builder/#exec-form-entrypoint-example) in the ENTRYPOINT. quotation marks can be escaped with backslashes.

### Let's see an example:

*entrypoint.sh*

Takes two variables (message and version) and prints them.

```
#!/usr/bin/env sh
set -euo pipefail

# Parameters:
# $1: Message
# $2: Version

printf 'Message is: %s\n' "${1}"
printf 'Version is: %s\n' "${2}"
```


*Dockerfile*

```
# To run:
# docker build . -f Dockerfile -t docker-entrypoint-test && docker run docker-entrypoint-test
FROM alpine

ENV MESSAGE="A message that contains spaces." \
    VERSION=1.4.7

COPY ./entrypoint.sh /usr/local/bin/entrypoint.sh
RUN chmod +x /usr/local/bin/entrypoint.sh

# We execute the entrypoint script using the shell to ensure that environment variables are expanded.
# See https://docs.docker.com/engine/reference/builder/#exec-form-entrypoint-example
ENTRYPOINT ["/bin/sh", "-c", "/usr/local/bin/entrypoint.sh \"${MESSAGE}\" ${VERSION}"]
```


You will see the following output if you build and run it:

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1619800920598/IskZE3AHT.png)

If you don’t use spaces around the MESSAGE variable in the ENTRYPOINT. You will see this output:

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1619800922352/PyXhlLu5z.png)

References:

* [https://unix.stackexchange.com/questions/131766/why-does-my-shell-script-choke-on-whitespace-or-other-special-characters](https://unix.stackexchange.com/questions/131766/why-does-my-shell-script-choke-on-whitespace-or-other-special-characters)

* [https://pubs.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_06_02](https://pubs.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_06_02)

* [https://pubs.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_06_05](https://pubs.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_06_05)