bash doubt

[L.V.Gandhi <lvgandhi@gmail.com>]

I have a script as follows
lvgandhi@lvghomepc:~$ cat bin/getlstocks
#!/bin/bash
i=0
while [ $i -ne 20 ]
do
        for trv in $(cat temp)
        do
                i=$i+1
                grep $trv stock/nsedata/2008/05/20080512.txt >> lstock
        done
done
when I run I get error as
integer expression expected
How to correct it

-- 
L.V.Gandhi
http://lvgandhi.tripod.com/
linux user No.205042