matlab.io.fits.getNumHDUs

Get number of HDUs in FITS file

Syntax

N = matlab.io.fits.getNumHDUs(fptr)


Description

N = matlab.io.fits.getNumHDUs(fptr) returns the number of completely defined HDUs in a FITS file. If a new HDU has just been added to the file, then that HDU is counted only if it has been closed or if data has been written to it. This function does not change the current HDU.

Examples

Get Number of HDUs in File

import matlab.io.*
fptr = fits.openFile("tst0012.fits");
N = fits.getNumHDUs(fptr)

N = 
5

fits.closeFile(fptr)

Tips

• This function corresponds to the fits_get_num_hdus (ffthdu) function in the CFITSIO library C API.

• To use this function, you must be familiar with the CFITSIO C interface. You can access the CFITSIO documentation at the CFITSIO website.

Extended Capabilities

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool. (since R2026a)

The matlab.io.fits.getNumHDUs function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

Version History

R2026a: Use function in thread-based environments

You can use this function in thread-based environments.