FIX: PAUSE Command with Input Redirection in FORTRAN (67098)

MORE INFORMATION

When input is redirected from a file and the only data read from the file is one MS-DOS command for a PAUSE statement, the program works correctly. The following short program gives an example:

Sample Code

      write(*,*) 'Before PAUSE'
      pause
      write (*,*) 'After PAUSE'
      end

Data file, TEST.DAT:

   Ver

Command line:

   C:\> TEST < TEST.DAT

Output:

   Before PAUSE
   Pause - Please enter a blank line (to continue) or a
     DOS command.

   MS-DOS Version x.xx

   After PAUSE
				

If another PAUSE statement is added to the program, only the command for the first PAUSE is executed. The program appears to read to the end of the redirection file when it encounters the first PAUSE. If a READ statement is added to the program after the PAUSE statement, as in the next example, the program again reads to the end of the file. In this case, ERROR 6501 is generated. Code:

      integer i
      write(*,*) 'Before PAUSE'
      pause
      write (*,*) 'After PAUSE'
      read(*,*) i
      write (*,*) i
      end
				

Data: Output: When the READ statement is before the PAUSE statement, the DOS command is not executed:

Code:

      integer i
      read(*,*) i
      write (*,*) i
      write(*,*) 'Before PAUSE'
      pause
      write (*,*) 'After PAUSE'
      end
				

Data: Output: These problems are caused by the PAUSE command not reading data from the redirection file in the same way a READ statement would.

Workarounds

Do not use redirection on a program with more than one PAUSE statement or a combination of PAUSE and READ statements.

Use the OPEN command to open a file to be used for input for READ statements.

Use calls to the C functions SYSTEM or SPAWNLP instead of PAUSE statements to execute DOS commands. For more information on these functions, see page 86 of the "FORTRAN Advanced Topics" manual for version 5.00 or the DEMOEXEC.FOR program included with versions 4.x and 5.00 of FORTRAN.

This problem does not occur in earlier versions of FORTRAN because the functionality of the PAUSE statement is different. In earlier versions, you are not allowed to execute DOS commands after a PAUSE.