Example Program

The following listing shows an example of how to use the CFITSIO routines in a C program. The error checking of the returned status value has been omitted for the sake of clarity. Refer to the cookbook.c program that is included with the CFITSIO distribution for other example programs.

This program creates a new FITS file, containing a FITS image. An `EXPOSURE' keyword is written to the header, then the image data are writen to the FITS file before closing the FITS file.

#include "fitsio.h"  /* required by every program that uses CFITSIO  */
main()
{
    fitsfile *fptr;       /* pointer to the FITS file; defined in fitsio.h */
    int status, ii, jj;
    long  fpixel = 1, naxis = 2, nelements, exposure;
    long naxes[2] = { 300, 200 };   /* image is 300 pixels wide by 200 rows */
    short array[200][300];

    status = 0;         /* initialize status before calling fitsio routines */
    fits_create_file(&fptr, "testfile.fits", &status);   /* create new file */

    /* Create the primary array image (16-bit short integer pixels */
    fits_create_img(fptr, SHORT_IMG, naxis, naxes, &status);

    /* Write a keyword; must pass the ADDRESS of the value */
    exposure = 1500.;
    fits_update_key(fptr, TLONG, "EXPOSURE", &exposure,
         "Total Exposure Time", &status);

    /* Initialize the values in the image with a linear ramp function */
    for (jj = 0; jj < naxes[1]; jj++)
        for (ii = 0; ii < naxes[0]; ii++)
            array[jj][ii] = ii + jj;

    nelements = naxes[0] * naxes[1];          /* number of pixels to write */

    /* Write the array of integers to the image */
    fits_write_img(fptr, TSHORT, fpixel, nelements, array[0], &status);

    fits_close_file(fptr, &status);            /* close the file */

    fits_report_error(stderr, status);  /* print out any error messages */
    return( status );
}