j2pp is a command-line text preprocessor that uses Jinja2 syntax: it reads an input file containing Jinja2 directives and outputs the result of template rendering. The command-line syntax tries to be remiscent of well-known UNIX text preprocessors like cpp and m4.

usage: j2pp.py [-h] [-V] [--selftest] [-v] [-D NAME[=VALUE]] [-I DIR]
               [-i INPUT] [-o OUTPUT]

A text file preprocessor using Jinja2 syntax: execute Jinja2
directives in the INPUT file, and write the result to the OUTPUT file.

Data to be substituted into the template is defined using the `-D
NAME=VALUE` option (see below).  Dots and "subscript" ([]) syntax is
correctly interpreted in the NAME part: i.e., given `-D NAME=VALUE`
you can refer to NAME in the input Jinja2 template to get back VALUE.
Lists are defined by repeated assignment to the same NAME: `-DNAME=1
-DNAME=2 -DNAME=3` will define `NAME` as the Jinja2 list `[1,2,3]`.

optional arguments:
  -h, --help            show this help message and exit
  -V, --version         Show program name and version and exit.
  --selftest            Run self-test routine and exit.
  -v, --verbose         Log program actions at increasing detail. Repeat
                        thrice or more for debug-level info.
  -D NAME[=VALUE], --define NAME[=VALUE]
                        Substitute VALUE for NAME in the input template. If
                        VALUE is not given, assume `1`.
  -I DIR, --search DIR  Search for referenced templates in the given DIR.
  -i INPUT, --input INPUT
                        Read input template from file INPUT. If omitted, the
                        input template is read from STDIN.
  -o OUTPUT, --output OUTPUT
                        Write output to file OUTPUT. If omitted, output is
                        written to STDOUT.

Example

Given this input file::

{# file TEST.in #}
Domain name: {{domain}}

L2 addresses (list):
{% for hwaddr in sys.hwaddrs -%}
* {{ hwaddr }}
{% endfor %}

IP network interfaces:
{% for ifname, ipv4addr in sys.ipv4.iteritems() -%}
* {{ ifname }}: {{ ipv4addr }}
{% endfor %}

when invoked in the following way, j2pp will produce this output::

$ ./j2pp.py \
    -D domain=example.org \
    -D sys.hwaddrs=11:22:33:44:55:66 \
    -D sys.hwaddrs=aa:bb:cc:dd:ee:ff \
    -D sys.ipv4addr[lo]=127.0.0.1 \
    -D sysipv4addr[docker0]=192.0.2.2 \
    -i TEST.in

Domain name: example.org

L2 addresses (list):
* 11:22:33:44:55:66
* aa:bb:cc:dd:ee:ff


IP network interfaces:
* lo: 127.0.0.1
* docker0: 192.0.2.2

Installation

Just copy the j2pp.py script anywhere in the shell's PATH. The Jinja2 Python module needs to be installed for it to work.