# HDF5 Software Controls

(Work in progress draft)

A descriptions knobs and turns such as environment variables and settings that controls the functionality of HDF5 libraries and tools. This is intended for HDF5 libraries and tools developers. HDF5 application users may consult the document A guide to debugging HDF5 API calls.

## Library Building Controls

### Environment variables

CC
  Used by configure. Override the default C compiler.
LIBS
  Used by configure. Add more libraries to be used.
NP
  Number of MPI-processes to invoke for testing. Default to 2.
HDF5_NOCLEANUP
  Used by most test programs. When set, temporary files created during tests are NOT removed. Default is to remove them by the end of each test. Note that the variable value does not matter. E.g., the values of "yes", "no" and "" all have the same effect, that is, NO cleanup.
H5FD_mpio_Debug
  Used by the MPIO file driver for debugging. Need to have H5FDmpio_DEBUG macro defined during compiling. Should be set to a string to turn on various tracing. Valid values (cases matter) are:
  t
    Trace all routine
  r
    Trace read routines
  w
    Trace write routines
  c
    Show result of MPI_Get_count
HDF5_MPI_OPT_TYPES
  Used by the MPIO file driver to control the use of the optimized mpi input/output routine. 0 turns it off, 1 turns it on (uses optimized code if it can).

### Compile Macros

H5FDmpio_DEBUG
  Compile macro. Compile in the MPIO file driver related debugging statements. Defined if macro H5F_DEBUG is defined.
H5FD_mpio_Debug
  Compile in debugging used by the MPIO file driver. Need to have H5FDmpio_DEBUG macro defined during compiling. Should be set to a string to turn on the tracing. See environment variable H5FD_mpio_Debug for valid values.

THG Help Desk: 'help' at hdfgroup.org
Last modified: December 11, 2000
Last modified: March 27, 2007 (Help Desk contact only)