Simple grader written in shell script

grader.sh

#!/bin/bash
ext=sol

if [ "$#" -lt 1 ]
then
	echo "Usage: $0 [executable] code [input_output_solution_folder]"
	exit 1
fi

if [ -x "`which "$1"`" ]
then
	bin=$1
	shift
else
	bin=java
fi

code=$1
if [ "$#" -lt 2 ]
then
	folder=.
else
	folder=$2
fi

THR=1 #Time Limit
sum=0
nCase=0
nT=0
nWrong=0
max=0
IFS=$'\n'
for input in `find "$folder" -name '*.in' | sort --version-sort`
do
	let nCase++
	sol="${input%in}$ext"
	time=`{ timeout "$THR" /usr/bin/time -f%e "$bin" "$code" < "$input" > /tmp/a; } 2>&1`
	if [ ! "$time" ]
	then
		echo -n T
		let nT++
	else
		if ! diff --ignore-trailing-space "$sol" /tmp/a >/dev/null
		then
			echo -n -
			let nWrong++

		else

			#basename "$input"
			#echo $time
			sum=`bc <<< "$sum+$time"`
			if [ `bc <<< "$max < $time"` -eq 1 ]
			then
				max="$time"
			fi
			if [ `bc <<< "$THR < $time"` -eq 0 ]
			then
				echo -n P
			fi
		fi
	fi
done

rm /tmp/a 2>/dev/null
echo
#echo sum: $sum
echo mean: `bc -l <<< "$sum /( $nCase - $nT )"`
echo max: $max
echo number of test case: $nCase
echo number of T case: $nT
echo number of - case: $nWrong