Path: utzoo!utgpu!attcan!uunet!husc6!bloom-beacon!gatech!ncar!noao!arizona!naucse!jdc
From: jdc@naucse.UUCP (John Campbell)
Newsgroups: comp.os.vms
Subject: Re: re: ftell & fseek
Message-ID: <827@naucse.UUCP>
Date: 4 Aug 88 15:14:07 GMT
References: <8808031204.AA26428@ucbvax.berkeley.edu>
Organization: Northern Arizona University, Flagstaff, AZ
Lines: 38

From article <8808031204.AA26428@ucbvax.berkeley.edu>, by LEICHTER@VENUS.YCC.YALE.EDU ("Jerry Leichter ", LEICHTER-JERRY@CS.YALE.EDU):
> 
> 	I was working on adapting a C program, currently running under UNIX,
> 	to VMS.  I had some problems with the use of "ftell" and "fseek" .
> 	After a call to "fseek" and a number 'n' of calls to "fgetc" are done,
> 	the next "ftell" don't return the actual position ( n bytes after the
> 	last "fseek"), but return the position of the last "fseek".  I think
> 	that could be some problems into the implementation of "fseek" and
> 	"getc" so that the pointer to the position into the file is not
> 	correctly handled by this functions.
> 
> On VMS, files may be record- or stream-oriented.  A record-oriented file,
> which is what you get by default, permits seeking only to the beginning of
> a record.
> 
> This is fully discussed in the VAX C documentation.
> 
> 							-- Jerry

Jerry has helped me a lot in the past (probably without remembering doing
so) and I don't want this comment to be construed as any criticism at all,
but...

There is a problem with ftell in VMS 'C' which thinking of things as record
oriented doesn't intuitively explain.  This "feature" has been discussed
on the net before--namely an fgets followed by an ftell (which all sounds
record-like) won't properly position you to the start of the record you
expect unless the file is a stream-lf file.  Current solutions include
doing an ungetc(fgetc(...)) prior to the ftell.  The first time I ran into
this I did not feel it was "fully discussed in the VAX C documentation".

As always, if you don't like this behavior, please submit an SPR to DEC
(I finally got an acknowledgement that they received one of the two I sent
in on this).
-- 
	John Campbell               ...!arizona!naucse!jdc

	unix?  Sure send me a dozen, all different colors.