[net.unix-wizards] lseek beyond EOF se-man-tic gripe

trb@floyd.UUCP (Andy Tannenbaum) (08/23/83)

According to the 4.1bsd (7th Edition) lseek(2) man page:

	Seeking far beyond the end of a file, then writing, creates a
	gap or `hole', which occupies no physical space and reads as
	zeros.

Pray tell, just how far beyond EOF must one seek before this feature
takes effect, and if not physical space, does it occupy some
transcendental space? ;-)

At least this man page tells you that the feature exists, the System
III/V manuals just ignore it.

	Andy Tannenbaum   Bell Labs  Whippany, NJ   (201) 386-6491

reha@orion.UUCP (R.GUR) (08/29/83)

Andy,
	This is in response to why the "gap" in files "feature" is documented
	in the 4.1BSD manuals and not the USG III and V manuals.

	I suspect that the 4.1 BSD manuals are descendents of the earlier
	V7 documents which had many details of the internal implementation
	of files within the kernel. I think that taking the implementation
	details (of files) out of the USG III and V manuals was a step in
	the right direction. 

	Ordinary programmers using files on UNIX should not use details on how
	files are handled within the kernel.  All that should be in the manual
	is that seeks beyond EOF are permitted. There should be a separate
	document entitled "The UNIX I/O System" or something like that to
	exhort the nitty gritty for "system programmers".


						orion!reha