LINUX:编写一个shell脚本，并利用函数实现数列求和运算

LINUX:编写一个shell脚本，并利用函数实现数列求和运算

#!/bin/sh
fun()
{
sum=0
for i in `seq $1 $2`
do
sum=`expr $i + $sum`
done
echo $sum
}
echo "Please input 2 number:"
read a b
expr $a + 0 1>/dev/null 2>&1
if [[ $? -ne 0 ]];then
echo "wrong number"
exit 1;
fi
expr $b + 0 1>/dev/null 2>&1
if [[ $? -ne 0 ]];then
echo "wrong number"
exit 1;
fi
if [[ $a -ge $b ]];then
echo "wrong number"
exit 1;
fi
fun $a $b

 #!/bin/bash
 sum=0
 if [ $# -ne 2 ]
 then
    echo "Please input two numbers!"
 elif [ $1 -gt $2 ]
 then
    echo "The seconde number must be  great the first number."
 else
     for i in $(seq $1 $2)
     do
       sum=`expr $sum + $i`
     done
     echo ""$1~$2" sum is $sum"
 fi
 #执行结果
#[root@localhost opt]# ./b.sh 3 6
#"3~6" sum is 18
#[root@localhost opt]# ./b.sh 3 
#Please input two numbers!
#[root@localhost opt]# ./b.sh 3 5 6
#Please input two numbers!
#[root@localhost opt]# ./b.sh 3 2
#The seconde number must be  great the first number.
#[root@localhost opt]# ./b.sh 3 25
#"3~25" sum is 322

#!/bin/bash
sum()
{
   total=0
   for num in `seq $1 $2`
   do
      let total+=num
   done
   echo $total
}   
read -p "Input number1: " num1
read -p "Input number2: " num2
if [ $num1 -ge $num2 ]; then
   echo "Wrong number!"
   exit 1
fi
sum $num1 $num2
exit 0

#!/bin/sh
#
#
sum(){
a=$1
b=$2
c=$a
while [ $c -le $b ]
do
sum=$(($sum+$c))
c=$(($c+1))
done
echo $sum
}
read -p "Please input the number1:" x
read -p "Please input the number2:" y
if [ $x -ge $y ];then
echo "wrong number!"
else
sum $x $y
fi
exit 0