how to write the wpa_supplicant.conf

[belle.shi at yy.com]

hi
  i use the wpa_gui to connect to wpa_supplicant, but when the ap uses 
shared wep, i can't connect to the wpa_supplicant, but after i add 
auth_alg=OPEN SHARED
in the wpa_supplicant.conf, everything qoes ok. but i think this is not 
a good way, i think if the wpa_supplicant can write the content 
"auth_alg=OPEN SHARED"
to the wpa_supplicant.conf automaticlly when wpa_supplicant found the 
current alg is wep? so i want to know how the wpa_supplicant to write 
the file wpa_supplicant.conf? where is the code?