How do I format a PRINT or WRITE statement to overwrite the current line on the console screen?

Question

I want to display the progress of a calculation done with a DO-loop, on the console screen. I can print out the progress variable to the terminal like this:

Answer 1

The following worked perfectly using g95 fortran:

      NF = NF + 1
      IF(MOD(NF,5).EQ.0) WRITE(6,42,ADVANCE='NO') NF, ' PDFs'//CHAR(13)
  42  FORMAT(I6,A)

gave: 5 PDFs

leaving the cursor at the #1 position on the same line. On the next update, the 5 turned into a 10. ASCII 13 (decimal) is a carriage return.

Answer 2

There is no solution to this question within the scope of the Fortran standards. However, if your compiler understand backslash in Fortran strings (GNU Fortran does if you use the option -fbackslash), you can write

  write (*,"(A)",advance="no") "foo"
  call sleep(1)
  write (*,"(A)",advance="no") "\b\b\bbar"
  call sleep(1)
  write (*,"(A)",advance="no") "\b\b\bgee"
  call sleep(1)
  write (*,*)
  end

This uses the backslash character (\b) to erase previously written characters on that line.

NB: if your compiler does not understand advance="no", you can use related non-standard tricks, such as using the $ specifier in the format string.

Answer 3

The following should be portable across systems by use of ACHAR(13) to encode the carriage return.

          character*1 creturn
    !   CODE::
          creturn = achar(13)  !  generate carriage return
    !   other code ...
          WRITE( * , 101 , ADVANCE='NO' ) creturn , i , npoint
101     FORMAT( a , 'Point number : ',i7,' out of a total of ',i7)

Answer 4

OPEN(6,CARRIAGECONTROL ='FORTRAN')
DO I=1,5
WRITE(6,'(1H+" ",I)') I
ENDDO