循环与结构化命令
最近正在看LinuxShell编程从初学到精通这本书，写的很详细，每一章节后面都有对应的习题，自己也亲手写了下，还有一部分没有写出来，不过正在努力。学习东西要学无止境，循序渐进，希望大家帮助优化下，或者给出更好的建议，谢谢支持！
１、使用for 循环计算１００以内所有偶数的和，然后用while循环和until循环来实现这个计算，比较哪种结构更简单；
for:
#!/bin/bash
#
#In addition to sum assigned value
sum=0
#Use the list for circulation calculated from 1 to 100 of all the sum of, and the value stored in sum
for i in {0..100..2}
do
# echo $i
let "sum+=i"
# echo $sum
done
echo "sum=$sum"
while:
#!/bin/bash
#
#In addition to sum assigned value
sum=0
i=0
#The use of counter control while circulation calculated from 1 to 100 of all the sum of, and the value stored in sum
while (( i <= 100 ))
do
let "sum+=i"
echo "sum=$sum"
let "i+=2"
echo "i=$i"
done
echo "sum=$sum"
until:
#!/bin/bash
#
#In addition to sum assigned value
sum=0
i=0
#The use of counter control while circulation calculated from 1 to 100 of all the sum of, and the value stored in sum
until (( i > 100 ))
do
let "sum+=i"
echo "sum=$sum"
let "i+=2"
echo "i=$i"
done
echo "sum=$sum"