[GSoC] Machine readable output from userland utilities

[Jonathan Anderson]

On 23 May 2014, at 10:13, Wojciech Puchar <wojtek at wojtek.tensor.gdynia.pl> wrote:
> ideas completely against unix simplicity.

I disagree quite vigorously. this proposal is very much like FreeBSD's sysctl vs Linux's sysfs. It might be against the Plan 9 way of doing things, but it would actually let us be "more unix than unix". Imagine:

$ ifconfig | filterBy "ether" " 3c:07:.*" | sortBy "ether" | output my_ifconfig.format   # or "json" or "xml" or ...

A pipeline of little tools, each doing one thing well: how much more unix can you get? Currently, every command-line tool has to do two or three things:
1. its primary job,
2. output some arbitrary text format (that you're never allowed to change because other tools scrape it) and
3. (optionally) parse arbitrary text formats generated by users or some other tool.

Task 2 is annoying: in order to usefully query command-line tools, I have to write a parser. The tool has binary data, I want binary data, but we have to go through a dump/parse dance in order for me to get the data. This is the approach (again, from Plan 9) that brings you Linux sysfs. Perhaps David would now like to comment on his cross-platform "how much battery do I have" experience. :)

Task 3 isn't just annoying, however, it's risky. If every tool implements its own string protocol parsing, we greatly increase the risk of unnoticed bugs. Better to centralize as much string parsing as possible into a single library, which can be rigorously analyzed (and optimized!).

Imagine if geom didn't have to speak XML natively, but rather used a supported-everywhere-in-base data structure that users could convert into XML if they need it. Desktop applications are going to start requiring structured data passing via kdbus-like interfaces (currently based on GLib's GVariant), so we might as well have a structured representation that we like and are able to provide ABI support for (and, in the kdbus case, can possibly be converted to/from GVariant as required).

Basically, I think this is an excellent GSoC project idea.


Jon
--
Jonathan Anderson

jonathan at FreeBSD.org
http://freebsd.org/~jonathan/