Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!cernvax!achille
From: achille@cernvax.UUCP (achille petrilli)
Newsgroups: comp.lang.fortran
Subject: Re: File handling in Fortran 77
Message-ID: <2540@cernvax.UUCP>
Date: 30 Aug 90 23:17:24 GMT
References: <1990Aug29.173235.9405@ux1.cso.uiuc.edu> <BURLEY.90Aug30024743@world.std.com> <55875@iuvax.cs.indiana.edu>
Organization: CERN, European Laboratory for Particle Physics
Lines: 48

In article <55875@iuvax.cs.indiana.edu> bomgard@copper.ucs.indiana.edu (Tim Bomgardner) writes:
>In article <BURLEY.90Aug30024743@world.std.com> burley@world.std.com (James C Burley) writes:
>>In article <1990Aug29.173235.9405@ux1.cso.uiuc.edu> mcdonald@aries.scs.uiuc.edu (Doug McDonald) writes:
>>
>>   This has always bothered me. A file is just a sequence of it, usually
>>   organized as bytes - a text file must be in "bytes".
>>		...
>>
>>You don't.  Standard Fortran is built on older and more baroque/primitive
>>file storage technology than C/UNIX.  Fortran allows systems to implement
>>		...
>>
>Rubbish.  The answer is right there in front of you.  Set RECL=1,
>ACCESS='DIRECT' in the open statement.  For those of you who don't
>believe me, I'll be happy to email you fortran implementations of get,
>put, and seek that use no tricks whatsoever.
>
A few comments about this method:
1) Some fortran implementation I know of put control information into the
	DIRECT access file to record the record length (e.g. Apollo's ftn at sr9.x).
	In this case you could generate easily a huge overhead (In the Apollo the
	overhead per record is a couple of bytes, 4 or 8 I don't remember).
2) If I remember correctly, the f77 standard does NOT specify in which units the
	RECL is specified. I just tried to write 3 direct/unformatted records on
	Ultrix with f77 and fort (the VAX/VMS compiler running under Ultrix), each record
	having a RECL=4. I include the source for people who want to try this:

        program main
        open(1,file='/tmp/jkl',
     +  form='unformatted',access='direct',recl=4,status='new')
        write(1,rec=1) 1
        write(1,rec=2) 2
        write(1,rec=3) 3
        close(1)
        end

	f77 produced a 12 bytes output file, fort a 48 bytes one. You can extrapolate
	what your RECL=1 would have produced in the 2 cases.
3) For DIRECT access, you have to specify the record number every record you
	read/write. That's not exactly a byte stream.
4) I'd guess the overhead WRT an equivalent C program should be enormous, given that
	every byte (or longword in the case of VAX fortran) written is treated as a record.

I wouldn't really bend fortran that way to do these sort of things, it's not meant
to do it simply.

Achille Petrilli
Management Information Systems