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Introduction to HDF5 HDF5 Reference Manual Other HDF5 documents and links | And in this document, the HDF5 User's Guide: Files Datasets Data Types Dataspaces Groups References Attributes Property Lists Error Handling Filters Caching Chunking Debugging Environment DDL Ragged Arrays

# HDF5 Library Environment Variables and Configuration Parameters

## 1. Environment Variables

The HDF5 library uses UNIX environment variables to control or adjust certain library features at runtime. The variables and their defined effects are as follows:

`HDF5_DEBUG`
  Defines a list of debugging switches documented in the Debugging section of the HDF5 User's Guide.
`HDF5_NOCLEANUP`
  When set to a non-empty value, the programs in the test directory do not remove temporary HDF5 data files. The default is for each test to remove the files before exit.
`HDF5_MPI_OPT_TYPES` (for parallel beta version only)
  When set to `1`, PHDF5 will use the MPI optimized code to perform parallel read/write accesses to datasets. Currently, this optimization fails when accessing extendable datasets. The default is not to use the optimized code.
`HDF5_MPI_1_METAWRITE` (for parallel beta version only)
  When set to `1`, PHDF5 will write the metadata via process 0 of each opened parallel HDF5 file. This should improve I/O throughput. The default is not to use this optimization.

## 2. Configuration Parameters

The HDF5 configuration script accepts a list of parameters to control configuration features when creating the Makefiles for the library. The command
`configure --help`
will display the current list of parameters and their effects.

Introduction to HDF5 HDF5 Reference Manual Other HDF5 documents and links | And in this document, the HDF5 User's Guide: Files Datasets Data Types Dataspaces Groups References Attributes Property Lists Error Handling Filters Caching Chunking Debugging Environment DDL Ragged Arrays

======= HDF5 Library Environment Variables and Configuration Parameters

# HDF5 Library Environment Variables and Configuration Parameters

## 1. Environment Variables

The HDF5 library uses UNIX environment variables to control or adjust certain library features at runtime. The variables and their defined effects are as follows:

Variable | Description
--- | ---
`HDF5_DEBUG` | Defines a list of debugging switches documented in the Debugging section of the HDF5 User's Guide.
`HDF5_NOCLEANUP` | If set then programs in the test directories do not remove temporary files. The default is for each test to remove the files before exit if the test succeeds but to leave the files if the test fails.
`HDF5_PREFIX` | The value of this variable is prepended to all temporary file names created by the test programs and separated from the base name of the file by a slash. The default is no prefix.

<ode>HDF5_DRIVER

This variable should hold the name of a low-level HDF5 file driver such as `sec2`, `stdio`, `core`, `split`, or `family`. The family driver also takes an optional real-valued family member size in MB which defaults to 1. If this variable is not set or empty then the library-defined default file driver is used (which can be set at configuration time with the H5F_LOW_DFLT cpp constant, usually `sec2`).

`HDF5_MPI_OPT_TYPES` | When set to `1`, parallel HDF5 will use the MPI-optimized code to perform parallel read/write accesses to datasets. Currently, this optimization fails when accessing extendable datasets. The default is not to use the optimized code.
`HDF5_MPI_1_METAWRITE` | When set to `1`, parallel HDF5 will write the metadata via process 0 of each opened parallel HDF5 file. This should improve I/O throughput. The default is not to use this optimization.

## 2. Configuration Parameters

The HDF5 configuration script accepts a list of parameters to control configuration features when creating the Makefiles for the library. The command
`configure --help`
will display the current list of parameters and their effects.

Last modified: 25 November 1998