17.2.138. MPI_File_seek

MPI_File_seek - Updates individual file pointers (noncollective).

17.2.138.1. SYNTAX

17.2.138.1.1. C Syntax

#include <mpi.h>

int MPI_File_seek(MPI_File fh, MPI_Offset offset,
     int whence)

17.2.138.1.2. Fortran Syntax (see FORTRAN 77 NOTES)

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_FILE_SEEK(FH, OFFSET, WHENCE, IERROR)
     INTEGER FH, WHENCE, IERROR
     INTEGER(KIND=MPI_OFFSET_KIND)   OFFSET

17.2.138.1.3. Fortran 2008 Syntax

USE mpi_f08
MPI_File_seek(fh, offset, whence, ierror)
     TYPE(MPI_File), INTENT(IN) :: fh
     INTEGER(KIND=MPI_OFFSET_KIND), INTENT(IN) :: offset
     INTEGER, INTENT(IN) :: whence
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

17.2.138.2. INPUT PARAMETERS

  • fh: File handle (handle).

  • offset: File offset (integer).

  • whence: Update mode (integer).

17.2.138.3. OUTPUT PARAMETER

  • IERROR: Fortran only: Error status (integer).

17.2.138.4. DESCRIPTION

MPI_File_seek updates the individual file pointer according to whence, which could have the following possible values:

o MPI_SEEK_SET - The pointer is set to offset.

o MPI_SEEK_CUR - The pointer is set to the current pointer position plus offset.

o MPI_SEEK_END - The pointer is set to the end of the file plus offset.

The offset can be negative, which allows seeking backwards. It is erroneous to seek to a negative position in the file. The end of the file is defined to be the location of the next elementary data item immediately after the last accessed data item, even if that location is a hole.

17.2.138.5. FORTRAN 77 NOTES

The MPI standard prescribes portable Fortran syntax for the OFFSET argument only for Fortran 90. FORTRAN 77 users may use the non-portable syntax

INTEGER*MPI_OFFSET_KIND OFFSET

where MPI_OFFSET_KIND is a constant defined in mpif.h and gives the length of the declared integer in bytes.

17.2.138.6. ERRORS

Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument.

Before the error value is returned, the current MPI error handler is called. For MPI I/O function errors, the default error handler is set to MPI_ERRORS_RETURN. The error handler may be changed with MPI_File_set_errhandler; the predefined error handler MPI_ERRORS_ARE_FATAL may be used to make I/O errors fatal. Note that MPI does not guarantee that an MPI program can continue past an error.