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From: bomgard@copper.ucs.indiana.edu (Tim Bomgardner)
Newsgroups: comp.lang.fortran
Subject: File Handling in Fortran 77
Message-ID: <56017@iuvax.cs.indiana.edu>
Date: 31 Aug 90 18:52:23 GMT
Sender: news@iuvax.cs.indiana.edu
Organization: Indiana University, Bloomington IN.
Lines: 94
References:

Wow.  I got a lot more responses to that post than I expected.  I'm
going to simply include the code here for anyone who wants it.  In
general, no, I don't know if it works on your particular machine, but
it should.  One writer claimed it would not work on VAX/VMS because
a VMS record length (RECL) is 4.  This is only partly true.  RECL 
denotes record length in processor dependent units for _unformatted_
files (4 on the VAX), but in _characters_ for formatted files.  I 
erroneously left FORM='FORMATTED' out of the list of open statement 
parameters because it doesn't matter on my system.

This code was compiled using Ryan-McFarland Fortran on a 386 PC running
DOS 3.3.  As far as I can tell, it works perfectly.  I uploaded it to
a VAX/VMS system, where it worked as is with the following caveat.
The file system (which insists on doing more for you than you may
want or need) created the file with the "Fortran carriage control"
attribute set.  This made it impossible to TYPE the output file.
Setting CARRIAGECONTROL='NONE' in the open statement cured this
problem.  In practical terms, this means the program is not portable.
We can argue about whether this is a Fortran problem or a problem
with VMS's file system philosophy.

c======================================================================
c The following (stripped down) routines provide a simple character-
c oriented file i/o facility modeled after C's getc, putc, etc.
c They are intended for illustrative purposes only.  They require 
c direct access to the file; if the operating system won't allow it, 
c that's not Fortran's fault.
c======================================================================
c
c Open a file in a specified mode.  Only 'r' mode is implemented
c here.  Only one file at a time can be opened.  No error checking is 
c performed.
c
      integer function fopen(filename, mode)
      character filename*(*), mode*(*)
      common /cio/ fileptr
      integer fileptr

      lun = 99
      open(unit=lun, file=filename, status='old', access='direct',
     &     form='formatted', recl=1)
      fileptr = 0
      fopen = lun
      return
      end

c======================================================================
c
c Position the file pointer.  Only C's SEEK_SET (beginning of file) is
c implemented.  No error checking is performed.
c
      integer function fseek(lun, offset, whence)
      integer lun, offset, whence
      common /cio/ fileptr
      integer fileptr

      fileptr = 0
      fseek = 0
      return
      end

c======================================================================
c
c Get a character from an open file.  No error checking is performed.
c
      integer function getc(lun)
      integer lun
      common /cio/ fileptr
      integer fileptr
      character*1 khar

      read(unit=lun, fmt=7, rec=fileptr) khar
7     format(a)
      fileptr = fileptr + 1
      getc = ichar(khar)
      return
      end

c======================================================================
c
c Write a character to an open file.  No error checking is performed.
c
      integer function putc(khar, lun)
      character*1 khar
      integer lun
      common /cio/ fileptr
      integer fileptr

      write(unit=lun, fmt=7, rec=fileptr) khar
7     format(a)
      fileptr = fileptr + 1
      putc = ichar(khar)
      return
      end