Docker build arguments

Dockerfile

FROM busybox
ARG MESSAGE
RUN echo $MESSAGE > message.txt

main.sh

#!/bin/bash

MESSAGE="Hello World"
DOCKER_TAG="message_arg"
TEMP_CONTAINER="message_temp"
FILE_NAME="message.txt"

docker build --build-arg MESSAGE="$MESSAGE" -t $DOCKER_TAG -f Dockerfile .

docker run --name $TEMP_CONTAINER $DOCKER_TAG /bin/true
docker cp $TEMP_CONTAINER:$FILE_NAME ./
docker rm $TEMP_CONTAINER

cat $FILE_NAME

usage.txt

./main.sh
Sending build context to Docker daemon  4.096kB
Step 1/3 : FROM busybox
 ---> 54511612f1c4
Step 2/3 : ARG MESSAGE
 ---> Using cache
 ---> 71b87fd2d159
Step 3/3 : RUN echo $MESSAGE > message.txt
 ---> Running in 7606574a5305
 ---> 414ec45901e6
Removing intermediate container 7606574a5305
Successfully built 414ec45901e6
Successfully tagged message_arg:latest
message_temp
Hello World