matlab.io.fits.readCard

Read header record of keyword

Syntax

card = matlab.io.fits.readCard(fptr,keyname)

Description

card = matlab.io.fits.readCard(fptr,keyname) returns the entire 80-character header record of a keyword, with any trailing blank characters removed. Specify keyname as a string scalar or character vector. The function returns card as a character vector.

Examples

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Read Headers in All HDUs in File

Open Live Script

Read the headers for the keyword NAXIS for all the HDUs 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);
    card = fits.readCard(fptr,"NAXIS");
    fprintf('HDU %d: "%s"\n',j,card)
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_card (ffgcrd) 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.readCard function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

Version History