h5open#

Purpose#

Open an HDF5 dataset and returns a file handle.

Format#

fh = h5open(fname, dname, mode)#

Parameters:

fname (string) – a name of HDF5 file to open.
dname (string) – a name of a dataset (or group) in HDF5 file. e.g. "/mydata".
mode (string) –
the mode with which to open the file. Valid options include:
- "read": open file for read, positioned at the first row.
- "update": open file for write, positioned at the first row.
- "append": open file for write, positioned at the end of the file.

Returns:

fh (scalar) – file handle for use with readr(), or writer().

Examples#

Create and write to an HDF5 dataset#

rndseed 2344;

// Define filename
fname = "testdata.h5";

// Define dataset in HDF5 file
dname = "/mydata";

// Define a size of 4 rows and 3 columns
r = 4;
c = 3;
dims  = r|c;

// Create a 4 row by 3 column  HDF5 dataset
call h5create(fname, dname, dims);

// Create a 2x3 matrix
x = { 1.1 2.2 3.3,
      4.4 5.5 6.6 };

// Define mode for opening file handle
mode = "update";

// Open a file handle
fh = h5open(fname, dname, mode);

// Write the data in 'x' to the first two rows
call writer(fh, x);

// Create a 2x3 matrix
y = { 10 20 30,
      40 50 60 };

// Write the data in 'y' to the final two rows
call writer(fh, y);

// Close the file handle
close(fh);

Read data written in Example 1#

// Define mode for opening file handle
mode = "read";

// Open a file handle
fh = h5open(fname, dname, mode);

// Read the first row
a  = readr(fh, 1);

// Read the second, third, and fourth rows
b  = readr(fh, 3);

// Close the file
call close(fh);

After the code above

a =  1.10  2.20  3.30

b =   4.4   5.5   6.6
     10.0  20.0  30.0
     40.0  50.0  60.0

Remarks#

The file handle must be closed with either the close() function or closeall when you are finished using it.
To read or write data to a file opened with h5open(), use readr(), and writer().
To read and write data to an HDF5 dataset without opening a file handle, use h5read() and h5write().
The function dataopen() can open file handles for reading and writing to HDF5 datasets and other file types.