Linux Shell编程从初学到精通-循环与结构化命令

Linux Shell编程从初学到精通-循环与结构化命令

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"