function hvalue,file,keyword,EXTEN=exten
;NAME:hvalue
;
;PURPOSE:look through the header of file to find the keyword specified and get 
;that value
;
;CALLING SEQUENCE:hvalue('file','keyword',EXTEN=exten)
;
;INPUTS: file: the fits file with a header
;        keyword: the header keyword that you want the value of 
;
;OPTIONAL KEYWORD:EXTEN : extention number of the header you want to read
; if not supplied, it will be set to 0
;
;OUTPUTS:value of the keyword - will always be a string
;
;SIDE EFFECTS:?
;
;RESTRICTIONS: you must convert any numerical values after this is called
;
;EXAMPLES: print, hvalue('sedIOC_1.fits', 'SM_POS ',EXTEN=3)
;
;MODIFICATION HISTORY:Started on 1/9/03 by Myra Blaylock
;
;------------------------------------
if N_params() LT 2 then begin
     print,'Syntax - keyword_value= hvalue( filename,keyword,[ EXTEN= #])' 
     return, -1
 endif

if not keyword_set(exten) then exten = 0

header=''
header=HEADFITS(file,EXTEN=exten)
line=''
hh = strtrim(header,2)
if size(keyword,/tname) NE 'STRING' then keyword = strtrim(keyword,2)
flag = strpos(hh,keyword)
g = where(flag NE -1, Ng)
if Ng NE 1 then begin
    Print,'Either no such keyword or more than one.'
    value=-999
 endif else begin 
 line=hh(g)
 value=strtrim(strmid(line,10 ,20),2)
endelse
return,value
end