Character Arrays

In MOIMP there is an array of characters--the NDF FITS extension. If HDSTRACE cannot accommodate a string in the space available it attempts to give the first few characters followed by an ellipsis to indicate only a part of the string is reported. Thus in the above trace only part of the first FITS header card is shown. Part of the anti-penultimate header is reported. The last two lines are blank and 'END' and are listed in full. These truncations are not very convenient. HDSTRACE provides a mechanism for placing each character-array element on a new line.

    % hdstrace moimp.more.fits newline eachline

    MOIMP.MORE.FITS  <_CHAR*80>
       FITS(31)  
        'SIMPLE  =                    T / Standard FITS format', ...
        'END'

    End of Trace.

To list the whole array specify nlines=all or give an NLINES with at least the number of array elements. Note the object need not necessarily be the array. Below we trace the MORE extension.¹

    % hdstrace moimp.more nlines=a newline eachline

    MOIMP.MORE  <EXT>
       FITS(31)       <_CHAR*80>      
        'SIMPLE  =                    T / Standard FITS format',
        'BITPIX  =                   32 / No. of bits per pixel',
        'NAXIS   =                    2 / No. of axes in image',
        'NAXIS1  =                  512 / No. of pixels',
        'NAXIS2  =                  512 / No. of pixels',
        'EXTEND  =                    T / FITS extension may be present',
        'BLOCKED =                    T / FITS file may be blocked',
        ' ',
        'BUNIT   = 'NORMALIZED       B  ' / Units of data values',
        'BSCALE  =   7.450580607332E-06 / Scaling factor: r = f*i + z',
        'BZERO   =   1.600000000000E+04 / Zero offset: r = f*i + z',
        ' ',
        'CRPIX1  =   1.000000000000E+00 / Reference pixel',
        'CRVAL1  =  -3.542080000000E+03 / Coordinate at reference pixel',
        'CDELT1  =   2.989460000000E+01 / Coordinate increment per pixel',
        'CTYPE1  = 'PIXELS           B  ' / Units of coordinate',
        'CRPIX2  =   1.000000000000E+00 / Reference pixel',
        'CRVAL2  =   1.173410000000E+04 / Coordinate at reference pixel',
        'CDELT2  =  -2.989460000000E+01 / Coordinate increment per pixel',
        'CTYPE2  = 'PIXELS           B  ' / Units of coordinate',
        ' ',
        'ORIGIN  = 'ESO-MIDAS'          / Written by MIDAS',
        'OBJECT  = 'created with pro'   / MIDAS desc.: IDENT(1)',
        ' ',
        'HISTORY  ESO-DESCRIPTORS START   ................',
        'HISTORY  'HEADER_VERS'    ,'C*1 '   ,    1,   13,'13A1',' ',' '',
        'HISTORY  06-APR-1990',
        'HISTORY',
        'HISTORY  ESO-DESCRIPTORS END     ................',
        ' ',
        'END'

    End of Trace.

The nlines=all facility should be used with care; select an individual component or a structure that does not contain a large array. The output from a data array such as found in a typical NDF will be huge.