9.3.7 Update Keyword Routines

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These update routines modify the value, and optionally the comment field, of the keyword if it already exists, otherwise the new keyword is appended to the header. A separate routine is provided for each keyword datatype. The `longstr' version has the same functionality as the `str' version except that it also supports the local long string keyword convention for strings longer than 68 characters. A null pointer may be entered for the comment parameter which will leave the comment field unchanged or blank. The flt, dbl, cmp, and dblcmp versions of this routine have the added feature that if the 'decimals' parameter is negative, then the 'G' display format rather then the 'E' format will be used when constructing the keyword value, taking the absolute value of 'decimals' for the precision. This will suppress trailing zeros, and will use a fixed format rather than an exponential format, depending on the magnitude of the value.  

  int fits_update_key_[str, longstr] / ffu[kys, kls]
      (fitsfile *fptr, char *keyname, char *value, char *comment,
       > int *status)

  int fits_update_key_[log, lng] / ffuky[lj]
      (fitsfile *fptr, char *keyname, DTYPE numval, char *comment,
       > int *status)

  int fits_update_key_[flt, dbl, fixflt, fixdbl] / ffuky[edfg]
      (fitsfile *fptr, char *keyname, DTYPE numval, int decimals,
       char *comment, > int *status)

  int fits_update_key_[cmp, dblcmp, fixcmp, fixdblcmp] / ffuk[yc,ym,fc,fm]
      (fitsfile *fptr, char *keyname, DTYPE *numval, int decimals,
       char *comment, > int *status)