according to gnudatalanguage#1645 that's what must be done to work on…

… windows too

src/pro/utilities/idlneturl__define.pro

@@ -95,8 +95,8 @@ function idlneturl::Get, buffer=buffer, filename=filename, string_array=string_a
   if self.ftp_connection_mode EQ 0 then curl_cmd+='--ftp-pasv '
 ; headers
   if ptr_valid(self.headers) and n_elements(*(self.headers)) gt 0 then begin
-     for i=0,n_elements(*(self.headers))-1 do begin
-        if strlen((*self.headers)[i]) gt 0 then curl_cmd+="-H '"+strtrim((*self.headers)[i],2)+"' "
+     for i=0,n_elements(*(self.headers))-1 do begin ; note below curl under Windows accept only "-quote see #1465
+        if strlen((*self.headers)[i]) gt 0 then curl_cmd+='-H "'+strtrim((*self.headers)[i],2)+'" ' ; was: if strlen((*self.headers)[i]) gt 0 then curl_cmd+="-H '"+strtrim((*self.headers)[i],2)+"' "
      endfor
   endif
 
@@ -128,7 +128,7 @@ function idlneturl::Get, buffer=buffer, filename=filename, string_array=string_a
 ; been downloaded. When we write this function directly in GDL using
 ; libcurl, things will be way esaier.
   curl_asyn_get_headers='curl -LI --silent --show-error --include '                                                             ; will get only headers
-  curl_asyn_get_headers+="--write-out '\n%{size_header}\n%{content_type}\n%{response_code}\n%{size_download}' "    ; we get some useful values
+  curl_asyn_get_headers+='--write-out "\n%{size_header}\n%{content_type}\n%{response_code}\n%{size_download}" '    ; we get some useful values
   cmd=curl_asyn_get_headers+id_cmd
   if KEYWORD_SET(verbose) then print, cmd
   SPAWN, cmd, result, blahblah
@@ -175,7 +175,7 @@ function idlneturl::Get, buffer=buffer, filename=filename, string_array=string_a
 ; number of bytes downloaded at each instant, aka progress_info[2]
 ; of course if the transfer encoding is not 'chunked'.
 
-     curl_asyn_get_all='curl -L --progress-bar -o '+filename+' ' ; will use progressbar values, but alas need output in external file.
+     curl_asyn_get_all='curl -L --progress-bar -o "'+filename+'" ' ; will use progressbar values, but alas need output in external file.
 ; remove /tmp/pb
      file_delete,'/tmp/pb',/allow_nonexistent,/quiet,/noexpand_path
 
@@ -206,7 +206,7 @@ no_callback:
 ; if there is no callback function, directly get the file as we do not
 ; need to be asynchronous. Best is to create the 'filename' directly.
 
-     curl_syn='curl -L --silent --show-error -o '+filename+' ' 
+     curl_syn='curl -L --silent --show-error -o "'+filename+'" ' 
      cmd=curl_syn+curl_cmd+id_cmd
      if KEYWORD_SET(verbose) then print, cmd
      SPAWN, cmd, result, blahblah

src/pro/utilities/n_bytes.pro

@@ -0,0 +1,52 @@
+function N_bytes,a
+;+
+; NAME:
+;       N_bytes()
+;
+; PURPOSE:
+;       To return the total number of bytes in data element
+;
+; CALLING SEQUENCE:
+;       result = N_bytes(a)
+;
+; INPUTS:
+;       a - any idl data element, scalar or array
+;
+; OUTPUTS:
+;       total number of bytes in a is returned as the function value
+;       (64bit longword scalar)
+; NOTES:
+;       (1) Not valid for object or pointer data types
+;       (2) For a string array, the number of bytes is computed after conversion
+;           with the BYTE() function, i.e. each element has the same length,
+;           equal to the maximum individual string length.
+;
+; MODIFICATION HISTORY:
+;       Version 1  By D. Lindler  Oct. 1986
+;       Include new IDL data types    W. Landsman          June 2001
+;       Now return a 64bit integer    W. Landsman          April 2006
+;-
+;-----------------------------------------------------
+;
+ dtype = size(a,/type)                      ;data type
+ if dtype EQ 0 then return,0            ;undefined
+ nel = N_elements(a)
+ case dtype of
+        1: nb = 1                            ;Byte
+        2: nb = 2                            ;16 bit signed integer
+        3: nb = 4                            ;32 bit signed integer
+        4: nb = 4                            ;Float
+        5: nb = 8                            ;Double
+        6: nb = 8                            ;Complex
+        7: nb = max(strlen(a))               ;String                      
+        8: nb = N_tags(a,/length)            ;Structure
+        9: nb = 16                           ;Double Complex
+       12: nb = 2                            ;Unsigned 16 bit Integer
+       13: nb = 4                            ;Unsigned 32 bit Integer
+       14: nb = 8                            ;64 bit signed integer
+       15: nb = 8                            ;64 bit unsigned integer
+     else: message,'ERROR - Object or Pointer data types not valid'
+ endcase
+
+ return,long64(nel)*nb
+ end