These routines modify the value of an existing keyword. An error is returned if the keyword does not exist. Wild card characters may be used when specifying the name of the keyword to be modified.
  int fits_modify_record / ffmrec
      (fitsfile *fptr, int keynum, char *card, > int *status)
 
  int fits_modify_card / ffmcrd
      (fitsfile *fptr, char *keyname, char *card, > int *status)
 
  int fits_modify_key_str / ffmkys
      (fitsfile *fptr, char *keyname, char *value, char *comment,
       > int *status);
  int fits_modify_key_[log, lng] / ffmky[lj]
      (fitsfile *fptr, char *keyname, DTYPE numval, char *comment,
       > int *status)
  int fits_modify_key_[flt, dbl, fixflt, fixdbl] / ffmky[edfg]
      (fitsfile *fptr, char *keyname, DTYPE numval, int decimals,
       char *comment, > int *status)
  int fits_modify_key_[cmp, dblcmp, fixcmp, fixdblcmp] / ffmk[yc,ym,fc,fm]
      (fitsfile *fptr, char *keyname, DTYPE *numval, int decimals,
       char *comment, > int *status)
 
  int fits_modify_key_null / ffmkyu
      (fitsfile *fptr, char *keyname, char *comment, > int *status)