This image is based on Alpine Linux image, which is only a 5MB image, and contains Bash (Bourne Again SHell) with some useful tools (e.g., complete implementations of grep, sed, awk, bc, head, tail, and etc).
Download size of this image is only:
$ docker run --rm frolvlad/alpine-bash bash -c 'echo "Hello World"'
Once you have run this command you will get printed 'Hello World' from Bash!