dcinja

The smallest binary size of template engine, born for docker image

Generate template file by powerful template engine inja. This project wrap it in docker command line binary.

For building docker image, smaller execution binary size should be better. The project dcinja compile by c++ compiler, the binary size is only 500KB ~ 600KB. It's very suitable to use dcinja in container to dynamic generate configuration file at run-time.

Dependency library

Binary size

arch	os	dcinja size	embedded libstdc++
linux-amd64	Ubuntu 16+, Debian stretch+	591KB	Y
alpine	alpine 3.9+	586KB	N (libstdc++.so 1.3MB+)

Command line usage

Reference repo docker example to build dcinja and copy to /bin/ as system command in docker image.

help description

  dcinja [OPTION...]

  -h, --help               print help
  -w, --cwd arg            change current working dir
  -s, --src arg            source template file path
  -d, --dest arg           dest template file path
  -e, --defines arg        define environment parameters, read system env when not assigned value, ex: `-e NAME=FOO -e NUM=1 -e MY_ENV`
      --force-system-envs  force to use system envs as final value
  -j, --json arg           define json content, ex: `-j {"NAME": "FOO"} -j {"PHONE": "123"}`
  -f, --json-file arg      load json content from file, ex: `-f p1.json -f p2.json`
  -v, --verbose            verbose mode

Template document

inja - document tutorial, It's compatiable with Jinja2.

variables {{ ... }}
statements {% ... %}
- for loop {% for key in data %} ... {% endfor %}
- condition {% if value >= 1 %} ... {% else if value >= 0 %} ... {% endif %}
- include {% include "xxx.template" %}
- assignment {% set name="test" %}
functions
- upper {{ upper("name") }}
- length {{ length(data_list) }}
- ...
comments {# ... #}

Example

input template from STDIN, output template to STDOUT

$ echo "TEST Name: {{ name }}" | dcinja -j '{"name": "Foo"}'
>>> TEST Name: Foo

input template from file, output template to file

$ dcinja -j '{"name": "Foo"}' -s input.template -d output.template

input json from file

$ dcinja -f param.json -s input.template -d output.template

define env from command line or system env

$ dcinja -e name=Foo -s input.template -d output.template
or
$ export name=Foo
$ dcinja -e name -s input.template -d output.template

parameter context priority: -e >> -j >> -f

-f: json file
-j: json content defiend in command line
-e: environment parameter defeind in command line or system
--force-system-envs: force to use system envs as final value

$ cat name.json
>>> {"name": "P1"}
$ echo "Name: {{ name }}" | dcinja -f name.json
>>> Name: P1
$ echo "Name: {{ name }}" | dcinja -j '{"name": "P2"}' -e name=P3 -f name.json
>>> Name: P3

Integration from release build

Dockerfile example, download dcinja into docker image /bin/ as command. The download path should follow Github release page to get latest release version.

ubuntu

FROM ubuntu:latest
RUN apt-get update && apt-get install -y wget
RUN cd /tmp \
        && wget https://github.com/Falldog/dcinja/releases/download/v1.3/dcinja-1.3.linux-amd64.tar.gz -O dcinja.tar.gz \
        && tar xzf dcinja.tar.gz \
        && cp dcinja /bin/

# testing, check dcinja working normal
RUN dcinja -h \
        && echo "Normal: {{ name }}" | dcinja -j '{"name": "TEST"}'

# ...

ubuntu (multi-stage)

FROM ubuntu:latest as dcinja-downloader
RUN apt-get update && apt-get install -y wget
RUN mkdir -p /app \
        && cd /app \
        && wget https://github.com/Falldog/dcinja/releases/download/v1.3/dcinja-1.3.linux-amd64.tar.gz -O dcinja.tar.gz \
        && tar xzf dcinja.tar.gz

FROM ubuntu:latest
COPY --from=dcinja-downloader /app/dcinja /bin/

# testing, check dcinja working normal
RUN dcinja -h \
        && echo "Normal: {{ name }}" | dcinja -j '{"name": "TEST"}'

# ...

alpine

FROM alpine:latest
RUN apk --no-cache add wget libstdc++
RUN cd /tmp \
        && wget https://github.com/Falldog/dcinja/releases/download/v1.3/dcinja-1.3.alpine.tar.gz -O dcinja.tar.gz \
        && tar xzf dcinja.tar.gz \
        && cp dcinja /bin/

# testing, check dcinja working normal
RUN dcinja -h \
        && echo "Normal: {{ name }}" | dcinja -j '{"name": "TEST"}'
# ...

Note

The binary size build by c++ compiler, it's platform sensitive, the minimum c++ compiler support is C++11. It will dependent with libstdc++.so.

ldd result at ubuntu 18.04

$ ldd dcinja
	linux-vdso.so.1 (0x00007ffe933a9000)
	libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f376bc40000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f376b8a2000)
	libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f376b68a000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f376b299000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f376c220000)

Need to make sure your environment have the correct c++ runtime on

Ubuntu

apt-get update
apt-get install libstdc++

(Only support ubuntu 16.04+)

Alpine

apk add libstdc++