Dynamically parse a Dockerfile to find the image used and run commands in that image. Useful for installing packages in the exact environment the app will run in.

npm_cmd_docker.sh

#!/bin/bash

### Keep the Gist updated!
# https://gist.github.com/skwid138/b360dbab95bee28a424f350301454092
###

# File paths
DOCKERFILE="Dockerfile"

# Extract the image used in the builder stage (case-insensitive)
IMAGE=$(grep -i "^FROM .* as \+builder" "$DOCKERFILE" | head -n 1 | awk '{ print $2 }')

# If not found with lowercase 'as', try with uppercase 'AS'
if [ -z "$IMAGE" ]; then
    IMAGE=$(grep -i "^FROM .* AS \+builder" "$DOCKERFILE" | head -n 1 | awk '{ print $2 }')
fi

# If still not found, try the first FROM statement
if [ -z "$IMAGE" ]; then
    echo "Warning: Builder stage not found, using the first FROM statement..."
    IMAGE=$(grep "^FROM " "$DOCKERFILE" | head -n 1 | awk '{ print $2 }')
fi

# Verify the image was found
if [ -z "$IMAGE" ]; then
    echo "Error: Could not determine the base image from the Dockerfile."
    exit 1
fi

echo "Using image: $IMAGE"

# Check if npm command is provided
if [ "$#" -lt 1 ]; then
    echo "Usage: $0 <npm-command>"
    echo "Example: $0 npm install package"
    exit 1
fi

# Build the npm command from arguments
NPM_COMMAND="$@"

# Include the .env file if it exists
if [ -f ".env" ]; then
    DOCKER_RUN_ARGS="--env-file .env"
else
    DOCKER_RUN_ARGS=""
fi

# Run the docker command with the specified npm command
docker run --rm \
    -v "$(pwd)/.:/usr/src/app/." \
    -w /usr/src/app \
    "$IMAGE" \
    $NPM_COMMAND

# Exit with the status of the last command
exit $?