On 09/27/2011 06:46 PM, Kent A. Reed wrote:
Andy and Sebastian:
I was/am just looking for consistency.
Sebastian cites the halcmd man page, which, it turns out, is
inconsistent with the output from halcmd if one asks for help linkps
or help linksp. Unfortunately, that's where I started.
I checked the manpage first and didn't look at the halcmd help until
now. I see what you mean now, the halcmd help is at odds with the
manpage, and that's not right.
Some quick experiments show that halcmd net accepts any number of '='
characters in arrows (1 or more), it sometimes talks about one and
sometimes two in the docs, and it sometimes produces one and sometimes
produces two in its output. I agree, that is inconsistent and that's a
bummer.
Still, the argument that it's ok to do things inconsistently because it
really doesn't matter rings hollow to me. One can never predict how
someone is going to use this stuff. The great beauty of the Unix
platform is the ease with which one can pipe data from one program to
another.
I think until someone cares enough to scrub all this inconsistency out
of the code and the various docs, you've got the right answer - accept both.
Hey, that reminds me of another Unix pattern, the Robustness Principle,
which helps you deal with inconsistent software like halcmd:
https://secure.wikimedia.org/wikipedia/en/wiki/Robustness_principle
Many of my favourite Unix tools are ones with totally predictable,
machine-parsable output, because that feature makes them
script-friendly. But some useful Unix tools are not that way, they make
human-parsable output that's annoying to parse with scripts. Some
tools, like git, straddle the line with varying degrees of success. I'd
say halcmd is towards the annoying to parse side of the spectrum, and
it never bothered me because i never tried to parse its output
programmatically.
I took a quick look around and it seems like there's no complete python
interface into hal. There's the hal python module which lets you
write userspace hal components in python, but it does not export all
halcmd-like functionality to manipulate and examine the hal wiring. It
certainly lacks documentation! Maybe hal.py and _hal.so could be
extended to export more of libemchal.so to python? Then you wouldnt
have to parse anything, you could examine the structures directly.
All this would have been over in 30 seconds if we had been talking over
a beer.
Yes, this got overblown and I'm sorry about that. Next time you're in
Colorado, come by Boulder for a beer!
--
Sebastian Kuzminsky
--
All of the data generated in your IT infrastructure is seriously valuable.
Why? It contains a definitive record of application performance, security
threats, fraudulent activity, and more. Splunk takes this data and makes
sense of it. IT sense. And common sense.
http://p.sf.net/sfu/splunk-d2dcopy2
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