;+
; This saves several data containers into the output file
; (keep file).  These must be spectrum data containers.  This is most
; often used in conjuction with <a href="getchunk.html">getchunk</a>.
;
; @param chunk {in}{required}{type=spectrum data container arry} The
; array of spectrum data containers to save.
;
; @examples
; Copy the input file to the keep file (this is currently only
; possible in line mode), one scan at a time (in a procedure or function).
;
; <pre>
;    scans=get_scan_numbers(/unique)
;    for i=0,(n_elements(scan)-1) do begin
;       a = getchunk(scan=scans[i])
;       putchunk, a
;       data_free, a
;    endfor
; </pre>
;
; @version $Id$
;-
pro putchunk, chunk
    compile_opt idl2

    if n_params() eq 0 then begin
        usage,'putchunk'
        return
    endif

    npts = data_valid(chunk,name=name)
    if name ne 'SPECTRUM_STRUCT' then begin
        message,'Only spectral line data can be saved',/info
        return
    endif

    if npts le 0 then begin
        message,'The first element of chunk is empty or not valid',/info
        return
    endif

    !g.lineoutio->write_spectra,chunk
end