Can I read the binary file from the give position?

Zhanghong_T_ · ‎06-09-2005

Hi all,

I want to realize the following function:

Firstly, I write a 'binary' file (real*8 data type), then I wish I can locate to any position of the file and read the correspondent data without read from the begin of the file? How can I do? My code is as following. Can anyone modify the code for me?

Thanks,

Zhanghong Tang

Code:

implicit none
real*8 a
integer i
open(1,file='test',form='binary')
do i=1,10000
  a=i
  write(1)a
enddo
call testreadfile(1)
close(1)
end

subroutine testreadfile(fileid)
integer i
integer fileid
do i=1,10000
  a=readfile(fileid,i)
enddo
end subroutine

real*8 function readfile(fileid,i)result(out)
integer fileid, i
! How can I read the ith data from the file without read all its former data?
! Thanks

end function

Steven_L_Intel1 · ‎06-09-2005

Read about the FSEEK library function in the Intel Fortran Libraries Reference.

Paul_Curtis · ‎06-09-2005

This excellent question illustrates the limitations of Fortran file i/o as compared to other languages. Perhaps someday Fortran will develop modern file i/o. In the meantime,Win32 API functions can completely replace the native F90 file i/o, with improved performance and total versatility (albeit a lack of portability). See the attached code, particularly SetFilePointer.

Zhanghong_T_ · ‎06-10-2005

Thank both of you very much!

Another question: Can the 32-bit system support the file size greater than 2G?

Thanks,

Zhanghong Tang

Steven_L_Intel1 · ‎06-10-2005

Yes.