1、shell的计算

#!/usr/bin/env bash

##计算##
result=`expr 2 - 100`
echo "$result"

result1=$((5+5))
echo "$result1"

result2=$[5+4]
echo $result2

let result3=2+4
echo $result3

2、for循环举例

for var in 1 2 3 4 5 6 7 8 9
    do
      echo "then is number is $var"
    done

for var1 in {10..19}
    do
      echo "then is number is $var1"
    done

for var2 in `seq 20 28`
    do 
       echo "then is numver is $var2"
    done