linux中 for语句和while语句计算1-100的和

 

1、for语句

[root@centos7 test2]# cat test.sh
#!/bin/bash
sum=0
for i in `seq $1`
do
let sum+=$i
done
echo "the sum of 1-$1 is: $sum"
[root@centos7 test2]# bash test.sh 100
the sum of 1-100 is: 5050
[root@centos7 test2]# bash test.sh 5
the sum of 1-5 is: 15

 

[root@centos7 test2]# cat test.sh
#!/bin/bash
sum=0
read -p "please input an integer: " num
if [[ $num =~ [^0-9] ]]; then
echo "input error."
exit 10
elif [ $num -eq 0 ]; then
echo "input error."
exit 20
else
for i in `seq 1 $num`; do
sum=$[$sum+$i]
done
echo $sum
fi
unset sum
[root@centos7 test2]# bash test.sh
please input an integer: abcd
input error.
[root@centos7 test2]# bash test.sh
please input an integer: 0
input error.
[root@centos7 test2]# bash test.sh
please input an integer: -3
input error.
[root@centos7 test2]# bash test.sh
please input an integer: 100
5050

 

1-100的和

[root@centos7 test2]# for ((i=1,sum=0; i<=100; i++)); do let sum+=$i; done
[root@centos7 test2]# echo $sum
5050

 

1-100中偶数的和

[root@centos7 test2]# for ((i=1,sum=0; i<=100; i++)); do [[ $[i%2] -eq 0 ]] && sum=$[$sum+$i]; done
[root@centos7 test2]# echo $sum
2550

 

1-100中奇数的和

[root@centos7 test2]# for ((i=1,sum=0; i<=100; i++)); do [[ $[i%2] -eq 1 ]] && let sum+=$i; done
[root@centos7 test2]# echo $sum
2500

 

 

2、while语句

[root@centos7 test2]# cat test.sh
#!/bin/bash
sum=0
a=1
while [ $a -le $1 ]
do
let sum+=$a
let a++
done
echo "the sum of 1-$1 is: $sum"
[root@centos7 test2]# bash test.sh 100
the sum of 1-100 is: 5050
[root@centos7 test2]# bash test.sh 3
the sum of 1-3 is: 6

 

1-100内所有奇数的和

[root@centos7 test2]# cat test.sh
#!/bin/bash
i=1
sum=0
while [ $i -le 100 ]; do
if [ $[i%2] -ne 0 ]; then
let sum+=$i
let i++
else
let i++
fi
done
echo $sum
[root@centos7 test2]# bash test.sh
2500

 

1-100内所有偶数的和

[root@centos7 test2]# cat test.sh
#!/bin/bash
i=1
sum=0
while [ $i -le 100 ]; do
if [ $[i%2] -eq 0 ]; then
sum=$[$sum+$i]
let i++
else
let i++
fi
done
echo $sum
unset sum
[root@centos7 test2]# bash test.sh
2550