15.2.7. Querying File Parameters

MPI_FILE_GET_GROUP returns a duplicate of the group of the communicator used to open the file associated with fh. The group is returned in group. The user is responsible for freeing group.

MPI_FILE_GET_AMODE returns, in amode, the access mode of the file associated with fh.

Example In Fortran 77, decoding an amode bit vector will require a routine such as the following:

SUBROUTINE BIT_QUERY(TEST_BIT, MAX_BIT, AMODE, BIT_FOUND) 
! 
!   TEST IF THE INPUT TEST_BIT IS SET IN THE INPUT AMODE 
!   IF SET, RETURN 1 IN BIT_FOUND, 0 OTHERWISE 
! 
    INTEGER TEST_BIT, AMODE, BIT_FOUND, CP_AMODE, HIFOUND 
    INTEGER L, LBIT, MATCHER, MAX_BIT 
    BIT_FOUND = 0 
    CP_AMODE = AMODE 
100 CONTINUE 
    LBIT = 0 
    HIFOUND = 0 
    DO L = MAX_BIT, 0, -1 
       MATCHER = 2**L 
       IF (CP_AMODE .GE. MATCHER .AND. HIFOUND .EQ. 0) THEN 
          HIFOUND = 1 
          LBIT = MATCHER 
          CP_AMODE = CP_AMODE - MATCHER 
       END IF 
    END DO 
    IF (HIFOUND .EQ. 1 .AND. LBIT .EQ. TEST_BIT) BIT_FOUND = 1 
    IF (BIT_FOUND .EQ. 0 .AND. HIFOUND .EQ. 1 .AND. & 
       CP_AMODE .GT. 0) GO TO 100 
END 

This routine could be called successively to decode amode, one bit at a time. For example, the following code fragment would check for MPI_MODE_RDONLY.

CALL BIT_QUERY(MPI_MODE_RDONLY, 30, AMODE, BIT_FOUND) 
IF (BIT_FOUND .EQ. 1) THEN 
   PRINT *, ' FOUND READ-ONLY BIT IN AMODE=', AMODE 
ELSE 
   PRINT *, ' READ-ONLY BIT NOT FOUND IN AMODE=', AMODE 
END IF