请大家帮帮忙 integer expression expected 问题 很急！！

winpad

这段shell在一个嵌入式系统上运行超过48小时，有很大几率出现integer expression expected的问题。请大家帮帮忙，看一下。
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#!/bin/sh
#try

try_1()
{
cd /xx/
find /xx/ ! -type d | xargs ls -trl | sed '/bak/d' | awk '{print $9}' | sed -n '1,6p' | xargs rm -f>/dev/null 2>&1  

delete
}

main()
{
sleep 5
choice
}

choice()
{

used=`df | awk '{if($1~/hda3/) print $4}'`
if [ "$used" = "" ];then
sleep 60
main
elif [ "$used" -lt "42000" ];then
delete
else
sleep 60
main
fi        
}
delete()
{
usedd=`df | awk '{if($1~/hda3/) print $4}'`
if [ "$usedd" -lt "50000" ];then
sleep 5
try_1
else
main
fi
}

main
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yongjian

1. [ "$used" -lt "42000" ]

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This is not the best way to compare integer.

1. [[ $userd < 42000 ]] OR (( $userd < 42000 ))

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should be more safer. "[]" will more likely get logic error than the rest two. Pls try and see...

winpad

thanks,have a try!