Prints Dockerfiles as JSON to stdout, optionally evaluates build args. Uses the official Dockerfile parser from buildkit. Plays well with jq.
Using go get:
go get -u github.com/keilerkonzept/dockerfile-jsonOr download the binary for your platform from the releases page.
dockerfile-json [PATHS...]
Usage of dockerfile-json:
-build-arg value
a key/value pair KEY[=VALUE]
-expand-build-args
expand build args (default true)
-jsonpath string
select parts of the output using JSONPath (https://goessner.net/articles/JsonPath)
-jsonpath-raw
when using JSONPath, output raw strings, not JSON values
-quiet
suppress log output (stderr)
Dockerfile
ARG ALPINE_TAG=3.10
FROM alpine:${ALPINE_TAG} AS build
RUN --network=host echo "Hello world" > abc
FROM build AS test
RUN --security=insecure echo "foo" > bar
FROM scratch
COPY --from=build --chown=nobody:nobody abc .
RUN --mount=type=bind,source=./abc,target=/def
CMD ["echo"]$ dockerfile-json Dockerfile | jq .{
"MetaArgs": [
{
"Key": "ALPINE_TAG",
"DefaultValue": "3.10",
"ProvidedValue": null,
"Value": "3.10"
}
],
"Stages": [
{
"Name": "build",
"OrigCmd": "FROM",
"BaseName": "alpine:3.10",
"Platform": "",
"Comment": "",
"SourceCode": "FROM alpine:${ALPINE_TAG} AS build",
"Location": [
{
"Start": {
"Line": 3,
"Character": 0
},
"End": {
"Line": 3,
"Character": 0
}
}
],
"As": "build",
"From": {
"Image": "alpine:3.10"
},
"Commands": [
{
"CmdLine": [
"echo \"Hello world\" > abc"
],
"Files": null,
"FlagsUsed": [
"network"
],
"Mounts": [],
"Name": "RUN",
"NetworkMode": "host",
"PrependShell": true,
"Security": "sandbox"
}
]
},
{
"Name": "test",
"OrigCmd": "FROM",
"BaseName": "build",
"Platform": "",
"Comment": "",
"SourceCode": "FROM build AS test",
"Location": [
{
"Start": {
"Line": 6,
"Character": 0
},
"End": {
"Line": 6,
"Character": 0
}
}
],
"As": "test",
"From": {
"Stage": {
"Named": "build",
"Index": 0
}
},
"Commands": [
{
"CmdLine": [
"echo \"foo\" > bar"
],
"Files": null,
"FlagsUsed": [
"security"
],
"Mounts": [],
"Name": "RUN",
"NetworkMode": "default",
"PrependShell": true,
"Security": "insecure"
}
]
},
{
"Name": "",
"OrigCmd": "FROM",
"BaseName": "scratch",
"Platform": "",
"Comment": "",
"SourceCode": "FROM scratch",
"Location": [
{
"Start": {
"Line": 9,
"Character": 0
},
"End": {
"Line": 9,
"Character": 0
}
}
],
"From": {
"Scratch": true
},
"Commands": [
{
"Chmod": "",
"Chown": "nobody:nobody",
"DestPath": ".",
"ExcludePatterns": null,
"From": "build",
"Link": false,
"Mounts": null,
"Name": "COPY",
"NetworkMode": "",
"Parents": false,
"Security": "",
"SourceContents": null,
"SourcePaths": [
"abc"
]
},
{
"CmdLine": [],
"Files": null,
"FlagsUsed": [
"mount"
],
"Mounts": [
{
"Type": "bind",
"From": "",
"Source": "",
"Target": "",
"ReadOnly": true,
"SizeLimit": 0,
"CacheID": "",
"CacheSharing": "",
"Required": false,
"Env": null,
"Mode": null,
"UID": null,
"GID": null
}
],
"Name": "RUN",
"NetworkMode": "default",
"PrependShell": true,
"Security": "sandbox"
},
{
"CmdLine": [
"echo"
],
"Files": null,
"Mounts": null,
"Name": "CMD",
"NetworkMode": "",
"PrependShell": false,
"Security": ""
}
]
}
]
}Dockerfile
FROM maven:alpine AS build
# ...
FROM build AS test
# ...
FROM openjdk:jre-alpine
# ...$ dockerfile-json --jsonpath=..As Dockerfile"build"
"test"Dockerfile
ARG ALPINE_TAG=3.10
ARG APP_BASE=scratch
FROM alpine:$ALPINE_TAG AS build
# ...
FROM build
# ...
FROM $APP_BASE
# ...Using jq:
$ dockerfile-json Dockerfile |
jq '.Stages[] | select(.From | .Stage or .Scratch | not) | .BaseName'"alpine:3.10"Using --jsonpath:
$ dockerfile-json --jsonpath=..Image Dockerfile"alpine:3.10"Using --jsonpath, --jsonpath-raw output:
$ dockerfile-json --jsonpath=..Image --jsonpath-raw Dockerfilealpine:3.10$ dockerfile-json --build-arg ALPINE_TAG=hello-world --jsonpath=..Image Dockerfile"alpine:hello-world"$ dockerfile-json --jsonpath=..BaseName Dockerfile"alpine:3.10"
"build"
"scratch"$ dockerfile-json --expand-build-args=false --jsonpath=..BaseName Dockerfile"alpine:${ALPINE_TAG}"
"build"
"${APP_BASE}"