Edits keywords in a FITS card array FTS1_EDKEY
’
Amend’
, ’
Delete’
, ’
Exist’
, ’
Move’
, ’
Rename’
, ’
Print’
, ’
Update’
, and ’
Write’
. Each element can be abbreviated to the initial
letter.
’
Amend’
acts as ’
Update’
if the keyword exists, but as ’
Write’
if the keyword is absent.
’
Delete’
removes a named keyword.
’
Exist’
reports TRUE to standard output if the named keyword exists in the header, and FALSE if the
keyword is not present.
’
Move’
relocates a named keyword to be immediately before a second keyword. When this
positional keyword is not supplied, it defaults to the END card, and if the END card is absent, the new
location is at the end of the headers.
’
Null’
nullifies the value of the named keyword. Spaces substitute the keyword’
s value.
’
Print’
causes the value of a named keyword to be displayed to standard output. This will be a blank
for a comment card.
’
Rename’
renames a keyword, using the value as the new keyword.
’
Update’
revises the value and/or the comment. If a secondary keyword is defined explicitly, the
card may be relocated at the same time. If the secondary keyword does not exist, the card being edited
is not moved. Update requires that the keyword being edited exists.
’
Write’
creates a new card given a value and an optional comment. Its location
uses the same rules as for the Move command.
The keywords ’
’
, ’
COMMENT’
, and ’
HISTORY’
are comment cards and do not have a
value.
The keyword must exist except for the Amend, Write, and Exist commands.
The new keywords are inserted immediately before each corresponding position keyword. If any name in it does not exist in FITS array, the consequences will be as follows. In the Write, Amend (new keyword), and Move edits its corresponding keyword will be inserted just before the END card or appended to FITS array when the END card does not exist; however, the card is not relocated for an Update or Amend (with an existing keyword) edit. If two or more new cards have the same position name, they will all be put just before the position name in the same order as they are in NAMES.
A positional keyword is used by the Move, Write, Amend, and Update editing commands.
’
$V’
means use the current value of the NAMES keyword. This makes it possible to
modify a comment, leaving the value unaltered. In addition $V(keyword) requests that the
value of the keyword given between the parentheses be assigned to the keyword being
edited. This positional keyword must exist and have a value for a Write edit; whereas the
FITS-header value is unchanged for Update if there are problems with this positional keyword.
edited.
For a Rename edit, VALUES has a different meaning; in this case it stores the replacement keyword name.
’
$C’
means use the current comment. In addition $C(keyword)
requests that the comment of the keyword given between the parentheses be assigned
to the keyword being edited. If this positional keyword does not exist the comment is
unchanged for Update, and is blank for a Write edit. ’
_CHAR’
, ’
_DOUBLE’
,
’
_INTEGER’
, ’
_LOGICAL’
, ’
_REAL’
. In addition there are two special values: ’
COMMENT’
to indicate that the card is a comment (so strictly it has no type), and ’
’
to
indicate that the data type is unknown, as occurs for a value defined by a reference keyword.
The length should be at least eight characters. "
Exist"
operation. When an error occurs during editing, warning messages are sent at the normal reporting level, and processing continues to the next editing command.
The FITS fixed format is used for writing or updating headers, except for double-precision
values requiring more space. The comment is delineated from the value by the string ’
/ ’
.
The comments in comment cards begin one space following the keyword or from column 10 whichever is greater.
At present the following reserved keywords are neither modifiable nor movable: SIMPLE, BITPIX, NAXIS, NAXISn, EXTEND, PCOUNT, GCOUNT, XTENSION, BLOCKED, and END. This is because order in the extension should be fixed and should not be changed by any routine. There is one exception: an END keyword may be appended if one does not exist.