The behaviour of systemctl.

[Aaron Sowry]

On Sun, Jun 19, 2011 at 06:43:46PM +0100, Martin Dengler wrote:
> On Sun, Jun 19, 2011 at 12:54:38PM +0200, Aaron Sowry wrote:
> > On Sun, Jun 19, 2011 at 10:03:05AM +0100, Martin Dengler wrote:
> > > Your point about column headers is taken (explicitly, in my mail) and
> > > bears no more repeating since there's a bug about it.
> > 
> > I didn't realise there was a bug for this, which is it?
> 
> You alluded to RH #713567 in [1], so I assumed that bug had this point
> in it.  Re-reading it, it does.

That bug has been closed.

> > > Your point about paging continues to be that you don't like it for the
> > > purist reason that unix-y tools shouldn't format their output.
> > 
> > This is not just purism for purism's sake.
> 
> You said tools paging their tty-destined output "irked the crap"[1]
> out of you and didn't otherwise disagree that other tools do this (and
> other things) based on tty-ness.  I'm not sure I was wrong to read
> that as a purist's lament given the additional code is trivial in
> length.

This is not a deposition, and I'm not here to discuss semantics. Whatever you
took "irked the crap" to mean, the intended meaning was that it bothers me as a
symptom of poor programming convention.

> > I think the point is being lost here somewhere.
> > [original paging-takes-code point]
> > [new points objecting to paging]
> 
> The original point and new points you just applied to the irkesome
> behaviour are simply not compelling:

Matter of opinion.

> that 50+ lines of pager-related C
> is somehow a fearsome vector for terrible bugs and must be excised

A blatant exaggeration of what was actually said.

If, however, you really feel that you require concrete
examples, earlier in the thread it was pointed out by Lennart that "Implicit
--full when using a pager has been the default since quite some time in
systemd." I'm assuming he meant "when not using tty", but whether that's a typo or
not, I'm not seeing this behaviour in F15 in either the tty or non-tty case
anyway. Assuming this is a bug and not just a misunderstanding, then this is
exactly the kind of thing I'm talking about when I say that extra logic to try
and be clever *is* indeed a vector for annoying bugs.

> or that the year-old chosen defaults for a new command can be changed
> with flags somehow impose a crippling learning curve.  Especially,
> given (like I said) the precedents and utility of the defaults (which
> you didn't argue with[2]).

Again, an exaggeration, but with a thread of truth to it. "alias
systemctl=systemctl --no-pager" has been suggested as an acceptable solution to
disable paged output, except then if I pipe through less, as per every
other command I use, I lose column headers. Do I need to add "--force-headers"
or something to my alias too? Possibly not crippling, but learning to have to do
this to get sensible output is certainly a learning curve.

> 2. You said[3] you disputed the utility of paging-by-default, which is
>    the behaviour I praised, and that I missed your dispute as to its
>    utility in [1], but, no, actually, you gave no reasons why it
>    wasn't useful in [1].  You just said it irked you, had a real
>    danger of scary bugs, and had a bug when no pager was present,
>    none of which are arguments for uselessness.

If I haven't made the disputes clear enough for you by now, then I'm afraid I'm
not sure what else I can say. Uselessness it probably not the point here though, the
point is all of the other downsides associated with such an implementation.
Paging is certainly useful, however "|less" is not a difficult thing to type.

/Aaron
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