FUNCTION dustem_read_isrf,file,silent=silent,Nisrf=Nisrf,help=help

;+
; NAME:
;   dustem_read_isrf
;
; PURPOSE:
;   reads information relating to the ISRF and associated wavelength grid
;
; CATEGORY:
;    DustEMWrap, Distributed, LowLevel, Initialization
;
; CALLING SEQUENCE:
;   st=dustem_read_isrf(file,nisrf=nisrf)
;
; INPUTS:
;    file  : input file to be read
;
; OPTIONAL INPUT PARAMETERS:
;
; OUTPUTS:
;    st   : dustem data structure
;
; OPTIONAL OUTPUT PARAMETERS:
;        Nisrf : number of elements in the wavelength grid where ISRF
;        is defined
;
; ACCEPTED KEY-WORDS:
;    help     : writes this help
;
; COMMON BLOCKS:
;    None
;
; SIDE EFFECTS:
;
; RESTRICTIONS:
;    The DustEM fortran code must be installed
;    The DustEMWrap IDL code must be installed
;
; PROCEDURES AND SUBROUTINES USED:  
;
; EXAMPLES:
;
; MODIFICATION HISTORY:
;    Evolution details on the DustEMWrap gitlab.
;    See http://dustemwrap.irap.omp.eu/ for FAQ and help.  
;-
  
IF keyword_set(help) THEN BEGIN
   doc_library,'dustem_read_isrf'
   st=0.
   goto,the_end
ENDIF
  
;        lambISRF(k) = val(1)
;        ISRF(k) = val(2)

readcol,file,lambisrf,isrf,silent=silent
nlines=n_elements(lambisrf)

one_st={lambisrf:0.,isrf:0.}
st=replicate(one_st,Nlines)

st.lambisrf=lambisrf
st.isrf=isrf


;IF getenv('DUSTEM_WHICH') EQ 'VERSTRAETE' THEN BEGIN
IF !dustem_which EQ 'VERSTRAETE' THEN BEGIN
  st=st(1:*)
  Nisrf=n_elements(st)
ENDIF
;IF getenv('DUSTEM_WHICH') EQ 'WEB3p8' THEN BEGIN
IF !dustem_which EQ 'RELEASE' THEN BEGIN
  st=st(1:*)
  Nisrf=n_elements(st)
ENDIF

;stop

the_end:
return,st

END