BUG: Opening More Than 61 Files in a FORTRAN Windows NT App

• Microsoft FORTRAN PowerStation 32 for Windows NT, version 1.0 and 4.0

SYMPTOMS

A FORTRAN PowerStation application on Windows NT can have only 61 files open at a time. Attempting to OPEN the file number 62 will produce the run- time error:

   error F6417: too many open files

CAUSE

The 64-file limit of the PowerStation for MS-DOS has been carried over to Powerstation for Windows NT. Three of these files are reserved for system use, leaving 61 files for the program to use.

RESOLUTION

Use WIN32 application programming interface (API) functions to perform some or all of your file I/O.

STATUS

Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

The following sample keeps 100 files open at the same time:

Sample Code #1

c Compile options needed: none c

      include 'IO.FI'
      program OPEN_TEST
      character*9 fname/'FILE.000 '/
      integer*4 j
      fname(9:9) = CHAR(0)  ! Append null character
      do j = 1,100
         write(*,*) fname
         call open(fname)
         write(fname(6:8),'(i3.3)') j ! Write file extension
      enddo
      end

      subroutine open(name)
      character*(*) name, buffer*16
      integer lcreat, handle, len
      data buffer/'Open many files.'/

      handle = lcreat(name, 0)         ! Create a new file
      len = lwrite(handle, buffer, 16) ! Write to file
      len = llseek(handle, 0, 0)       ! Seek to the beginning
      len = lread(handle, buffer, 16)  ! Read data back from file
      end

Sample Code #2

C Open an existing file

      interface to integer function lopen
     +  [stdcall, alias:'__lopen@8'](filename, mode)
      character*1 filename[reference] ! null terminated file name
      integer mode[value] ! 0 = read-only, 1 = write-only
                          ! 2 = read-write
      end

      interface to integer function lcreat
     +  [stdcall, alias:'__lcreat@8'](filename, mode)
      character*1 filename [reference] ! null terminated file name
      integer mode[value] ! 0 = read-write, 1 = read-only
                          ! 2 = hidden, 3 = system
      end

      interface to integer function lclose
     +  [stdcall, alias:'__lclose@4'](handle)
      integer handle[value]
      end

      interface to integer function llseek
     +  [stdcall, alias:'__llseek@12'](handle,offset,origin)
      integer handle[value]
      integer offset[value] ! number of bytes to move pointer
      integer origin[value] ! 0 = beginning, 1 = current position
                            ! 2 = end of the file
      end

      interface to integer function lread
     +  [stdcall, alias:'__lread@12'](handle,buffer,length)
      integer handle[value]
      character*1 buffer
      integer length[value]  ! number of bytes
      end

      interface to integer function lwrite
     +  [stdcall, alias:'__lwrite@12'](handle,buffer,length)
      integer handle[value]
      character*1 buffer
      integer length[value]
      end