O: SXADDHIST

NAME

SXADDHIST

PURPOSE

Procedure to add HISTORY (or COMMENT) line(s) to a FITS header

EXPLANATION

The advantage of using SXADDHIST instead of SXADDPAR is that with 
SXADDHIST many HISTORY or COMMENT records can be added in a single call.

CALLING SEQUENCE

sxaddhist, history, header, [ /PDU, /COMMENT ]

INPUTS

history - string or string array containing history or comment line(s)
       to add to the FITS header

INPUT/OUTPUT

header - FITS header (string array).   Upon output, it will contain the
        specified HISTORY records added to the end

OPTIONAL KEYWORD INPUTS

/BLANK - If specified then blank ('       ') keywords will be written
       rather than 'HISTORY ' keywords.
/COMMENT - If specified, then 'COMMENT ' keyword will be written rather
       than 'HISTORY ' keywords.    
       Note that according to the FITS definition, any number of 
       'COMMENT' and 'HISTORY' or blank keywords may appear in a header,
       whereas all other keywords may appear only once.   
LOCATION=key - If present, the history will be added before this
       keyword.  Otherwise put it at the end.
/PDU - if specified, the history will be added to the primary
       data unit header, (before the line beginning BEGIN EXTENSION...)               
       Otherwise, it will be added to the end of the header.
       This has meaning only for extension headers using the STScI
       inheritance convention.

OUTPUTS

header - updated FITS header

EXAMPLES

sxaddhist, 'I DID THIS', header      ;Add one history record
hist = strarr(3)
hist[0] = 'history line number 1'
hist[1[ = 'the next history line'
hist[2] = 'the last history line'
sxaddhist, hist, header              ;Add three history records

SIDE EFFECTS

Header array is truncated to the final END statement
LOCATION overrides PDU.

HISTORY

D. Lindler  Feb. 87
April 90  Converted to new idl  D. Lindler
Put only a single space after HISTORY   W. Landsman  November 1992
Aug. 95   Added PDU keyword parameters
LOCATION added.  M. Greason, 28 September 2004.
Missing minus sign (1 -> -1) in testing for WHERE output when 
 looking for location to insert a comment  M. Haffner Oct 2012