replacekey - replace keywords in a FITS header

       The  user can provide a new_keyword, an old_keyword, a value and a comment.  replacekey first searchs for
       old_keyword  if  provided.  If  it  finds  it,  it  replaces  the  associated  card  by   the   new   one
       (new_keyword=value/comment).   If old_keyword is either not found or not provided, replacekey searchs for
       new_keyword, and if it finds it, replaces the associated card by the new one (new_keyword=value/comment).
       new_keyword has to be provided.

       Examples: You want to change the value of VALUE from 32 to 16 in myfile.fits: % replacekey -k "VALUE"  -v
       "16" myfile.fits

       If  you  want  to  replace  the  card  with  the  keyword  OLD by "NEW = 3.14 / This is a usefull key" in
       myfile.fits: % replacekey -k "NEW" -v "3.14" -c "This is a usefull key" -K "OLD" myfile.fits

       If your do not care about the HISTORY cards you have in the header, and want to replace the first one  by
       VALUE=32, you would do:
       % replacekey -k "VALUE" -v "32" -K "HISTORY" myfile.fits

       Modifications are so far only possible in the main header, not in the extensions.

                                                   28 Oct 1999                                     replacekey(1)

replacekey is aimed at replacing keywords in a FITS file's header by new keywords provided by the user on
       the command-line.

       Files shall all comply with FITS format

       replacekey - replace keywords in a FITS header

-kor--keykey
              To provide the new keyword.

       -Kor--oldkey
              To provide the old keyword.

       -vor--valval
              To provide the new value.

       -cor--comcom
              To provide the new comment.

hierarch28 to convert HIERARCH ESO keywords to regular 8-char keywords.

replacekey [options] <in>