### astSetFitsU

Store an undefined keyword value in a FitsChan

#### Description:

This function stores an undefined value for a named keyword within a FitsChan at the current card position. The new undefined value can either over-write an existing keyword value, or can be inserted as a new header card into the FitsChan.

#### Synopsis

void astSetFitsU( AstFitsChan $\ast$this, const char $\ast$name, const char $\ast$comment, int overwrite )

#### Parameters:

##### this
Pointer to the FitsChan.
##### name
Pointer to a null-terminated character string containing the FITS keyword name. This may be a complete FITS header card, in which case the keyword to use is extracted from it. No more than 80 characters are read from this string.
##### comment
A pointer to a null terminated string holding a comment to associated with the keyword. If a NULL pointer or a blank string is supplied, then any comment included in the string supplied for the " name" parameter is used instead. If " name" contains no comment, then any existing comment in the card being over-written is retained. Otherwise, no comment is stored with the card.
##### overwrite
If non-zero, the new card formed from the supplied keyword name and comment string over-writes the current card, and the current card is incremented to refer to the next card (see the " Card" attribute). If zero, the new card is inserted in front of the current card and the current card is left unchanged. In either case, if the current card on entry points to the " end-of-file" , the new card is appended to the end of the list.

#### Notes:

• If, on exit, there are no cards following the card written by this function, then the current card is left pointing at the " end-of-file" .

• An error will be reported if the keyword name does not conform to FITS requirements.