CheckVarMask Subroutine

  subroutine CheckVarMask(filename, varname, haveMask, missingval, rc)

! ARGUMENTS:
    character(len=*),  intent(in) :: filename
    character(len=*),  intent(in) :: varname
    logical, intent(out)          :: haveMask
    real(ESMF_KIND_R8)            :: missingval
    integer, optional             :: rc

    integer :: ncStatus
    integer :: gridid, varid
    character(len=128) :: errmsg
    integer, parameter :: nf90_noerror = 0

#ifdef ESMF_NETCDF
    rc = ESMF_FAILURE
 
    ! check if varname exist for GRIDSPEC and UGRID
    ! varname could be a list of variables separated by comma, need to check all of 
    ! them
    ncStatus = nf90_open (path=filename, mode=nf90_nowrite, ncid=gridid)
    errmsg = 'Fail to open '//trim(filename)
    if (CDFCheckError (ncStatus, &
            ESMF_METHOD, &
            ESMF_SRCLINE,&
            errmsg, &
            rc)) return
    ncStatus = nf90_inq_varid(gridid, varname, varid)
    errmsg = 'Variable does not exist '//trim(varname)
    if (CDFCheckError (ncStatus, &
            ESMF_METHOD, &
            ESMF_SRCLINE,&
            errmsg, &
            rc)) return
    ! Get missing value attribute
    ncStatus = nf90_get_att(gridid, varid, "_FillValue", missingval)
    if (ncStatus /= nf90_noerror) then
       ncStatus = nf90_get_att(gridid, varid, "missing_value", missingval)
       if (ncStatus == nf90_noerror) then
                   haveMask = .TRUE.
       else
                   haveMask = .FALSE.
       endif
     else
         haveMask = .TRUE.
     endif
     if (.not. haveMask) missingval = 0.0
     ncStatus = nf90_close(gridid)
     if (CDFCheckError (ncStatus, &
              ESMF_METHOD, &
              ESMF_SRCLINE,&
              errmsg, &
              rc)) return
     rc = ESMF_SUCCESS
     return
#else
     call ESMF_LogSetError(ESMF_RC_LIB_NOT_PRESENT, &
                 msg="- ESMF_NETCDF not defined when lib was compiled", &
                 ESMF_CONTEXT, rcToReturn=rc)
     return
#endif
  end subroutine CheckVarMask