Path: utzoo!utgpu!attcan!uunet!husc6!rutgers!ucsd!ucbvax!CITHEX.CALTECH.EDU!carl
From: carl@CITHEX.CALTECH.EDU (Carl J Lydick)
Newsgroups: comp.os.vms
Subject: Re: ftell & fseek
Message-ID: <880801033703.110b@CitHex.Caltech.Edu>
Date: 1 Aug 88 10:50:33 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 22

First, I'm sending this to INFO-VAX because my system never heard of the
node AGR04.TO.CNR.IT.

 > 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.

In section 2.5.3 of the VAX-C Run-Time  Library  Reference  Manual,  ftell  is
documented as follows:
        The ftell function measures the offset from the  beginning  of
        the  file.   With  record  files,  ftell  returns the starting
        position of the current record, not the current byte offset.
I think that the category "record files" doesn't  include  stream  files.   It
should  also  be  noted  that,  except  for  the first record of a file, ftell
considers the current record to be the last record from which data  was  read;
this  means  that  if you read one record in its entirety, do an ftell then an
fseek, you'll be back at the beginning of the record you just  read.  You  can
get around this by doing an ungetc(getc()) just before the call to ftell.