User's Guide

File Positioning

Figure 24. Position of the File Pointer When a File Is Opened with No POSITION= Specifier

-qposition suboptions	Implicit OPEN		Explicit OPEN
			STATUS = 'NEW'		STATUS = 'OLD'		STATUS = 'UNKNOWN'
	File exists	File does not exist	File exists	File does not exist	File exists	File does not exist	File exists	File does not exist
option not specified	Start	Start	Error	Start	Start (1), (3)	Error	Start	Start
appendold (2)	Start	Start	Error	Start	End	Error	Start	Start
appendunknown	Start	Start	Error	Start	Start (3)	Error	End	Start
appendold and appendunknown	Start	Start	Error	Start	End	Error	End	Start

The important things to note are:

(1) The behavior of the xlf90, xlf90_r, xlf90_r7, xlf95, xlf95_r, and xlf95_r7 commands when you do not specify an option is different from XL Fortran Version 2.3 in this case. The Fortran 90 and Fortran 95 standards require this behavior. To minimize migration problems, the xlf, xlf_r, and xlf_r7 commands keep the same default as XL Fortran Version 2.3, and append to the end of the file.

Attention: If your program depends on the old behavior to append to the end of an existing file with STATUS='OLD', you need to use the option -qposition=appendold or POSITION= specifiers when making the switch to the xlf90, xlf90_r, xlf90_r7, xlf95, xlf95_r, or xlf95_r7 command. Otherwise, when you compile the program with these commands and run it, the new data will overwrite the file instead of appending to it.

(2) -qposition=appendold produces the default XL Fortran Version 2.3 behavior for positioning the file pointer. This option is in the configuration-file stanza for the xlf, xlf_r, and xlf_r7 commands, but not for the xlf90, xlf90_r, xlf90_r7, xlf95, xlf95_r, and xlf95_r7 commands.

(3) This file position was not possible in XL Fortran Version 2.3.

Preserving the XL Fortran Version 2.3 File Positioning

If you are upgrading from XL Fortran Version 2.3, and want the file positioning to work the same way as before, note the following guidelines:

• As long as you continue to use the xlf_r, xlf_r7, and xlf commands, you do not need to make any changes.

• When you make the transition to the xlf90, xlf90_r, xlf90_r7, xlf95, xlf95_r, and xlf95_r7 commands:

  • Add -qposition=appendold for programs that were previously compiled without any -qposition option.

  • Add -qposition=appendold:appendunknown for programs that were previously compiled with -qposition=append.