Re: [9fans] weird print(2) problems...

[forsyth@vitanuova.com]

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>>that if write(2) sees a zero length argument, it should consider that a
>>nop and return.  But then it seems that that would break some weird
>>semantic somewhere (``Any write will update a timestamp; except for
>>zero length writes, which are ignored.'' ``Dude, that's broken.'')

it isn't only the possible effect on time stamps; i think it
should do a write 0 because it's what you said to do.
to be fair, it's disguised by print, but even so,
if i wanted nop() i'd use
	;
or
	void nop(void){}
but i wouldn't call write() or even print.  i'd call write() when i wanted to write,
and i prefer systems that do what i tell it, so that if i say `write 0 bytes'
i expect it to do that, rather than adding yet
more special cases to remember.   the effect of writing 0 bytes
is determined by the device, but that's true of writing 1 byte or many,
so there's no difference there.

on the other hand, i'd probably write
	if(*str)
		print("%s", str);
if that's what i wanted.


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To: 9fans@cse.psu.edu
Cc: 
Subject: Re: [9fans] weird print(2) problems...
Date: Wed, 5 Sep 2001 10:22:18 -0400 (EDT)
Message-ID: <200109051422.KAA02761@augusta.math.psu.edu>

In article <20010904190825.3180.qmail@f.bio.cse.psu.edu> you write:
>Hm.  Pipes in Plan 9 preserve write boundaries, right?  Print is probably
>sending a zero length write, and confusing programs that interpret it
>as eof.

Hmm, that seems plausible.  It's also rather annoying; it seems to me
that if write(2) sees a zero length argument, it should consider that a
nop and return.  But then it seems that that would break some weird
semantic somewhere (``Any write will update a timestamp; except for
zero length writes, which are ignored.'' ``Dude, that's broken.'')

Is there an elegant solution (other than ``don't do print("");'',
since that might really mean ``don't do,

	read(0, str, 128);
	trimwhitespace(str);
	print("%s", str);

where the only thing read is a blank line or something.'')?

	- Dan C.