matlab.io.fits.readKey

Read key value

Syntax

[value,comment] = matlab.io.fits.readKey(fptr,keyname)

Description

[value,comment] = matlab.io.fits.readKey(fptr,keyname) returns the specified key value and comment. Specify the keyname argument as a string scalar or character vector. The function returns value and comment as character vectors.

Examples

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Read Key Values

Open Live Script

Read the key values and comments for all instances of the keyword NAXIS in a sample FITS file.

import matlab.io.*
fptr = fits.openFile("tst0012.fits");
N = fits.getNumHDUs(fptr);
for j = 1:N
    fits.movAbsHDU(fptr,j);
    [value,comment] = fits.readKey(fptr,"NAXIS");
    fprintf('HDU %d: NAXIS %s, "%s"\n',j,value,comment)
end

HDU 1: NAXIS 2, "No. of axes in matrix"
HDU 2: NAXIS 2, "Binary tables have 2 axes"
HDU 3: NAXIS 13, "A total of 13 axes !!!"
HDU 4: NAXIS 3, "Three axes"
HDU 5: NAXIS 2, "ASCII tables has 2 axes"

fits.closeFile(fptr)

Tips

This function corresponds to the fits_read_key_str (ffgkys) 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

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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.readKey function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

Version History