Docker build with template

dockerbuild.in.py

#! /usr/bin/env python
"""
<usage> ./dockerbuild.in <dockerfile.in> [dockerfile.in variables...] [docker build options...]

dockerfile.in variables can be passed in a format of "var:=value".

For example, if Dockerfile.in is the following:

```
FROM ubuntu:{ubuntu_version}
RUN apt-get update
```

`dockerfile.in`s option should be like:


```
./dockerfile.in Dockerfile.in ubuntu_version:=16.04 [docker build options...]
```

, then it will generates the following Dockerfile, and build it.

```
FROM ubuntu:16.04
RUN apt-get update
```
"""


import sys
import tempfile
import subprocess
import os
import shutil

def main():
    av = sys.argv[2:]
    dockerin = sys.argv[1]
    rest = []
    var = {}
    for v in av:
        var_val = v.split(":=")
        if len(var_val) == 2:
            var[var_val[0]] = var_val[1]
            continue
        rest.append(v)

    str_dockerfile = open(dockerin, 'r').read().format(**var)
    name_dockerfile = None
    dockerdir = tempfile.mkdtemp()
    dockerfile = os.path.join(dockerdir, 'Dockerfile')
    with open(dockerfile, 'w') as fd:
        fd.write(str_dockerfile)

    print "Generated docker file --------------------------------------------------------"
    print str_dockerfile
    print "------------------------------------------------------------------------------"
    cmd = ['docker', 'build', dockerdir] + rest
    print "Run docker build with the following commands ---------------------------------"
    print cmd
    print "------------------------------------------------------------------------------"
    p = subprocess.Popen(cmd)
    p.communicate()
    shutil.rmtree(dockerdir)
    
if __name__ == '__main__':
    main()