11.read命令

1.等待输入的值，赋给read后面的变量

printf "请输入一个数："
read num
printf "请再输入一个数："
read num1
pirntf "num=%s\nnum1=%s\n" "$num"  "$num1"

12.整数基本运算

1.算术运算+ ，- ，* ， /， %

value1=1
value2=2
value3=`expr $value1 + $value2`
value4=`expr $value1 - $value2`
value5=`expr $value1 \* $value2`  //乘法必须这么写
value6=`expr $value1 / $value2`
value=`expr $value1 % $value2`

num1=3
num2=4
#sum=$((num1+num2))
let sum1=num1+num2
echo $sum1

注意：$()和``代表取出数据的结果集
2.关系运算符 >、>=、<、<=、==、！=
注意：>、<、>=、<= 前面都需要加\才可以使用

value1=2
value2=3
result1=`expr $value1 \>= $value2`
result2=`expr $value1  \== $value2`
result3=`expr $value1 \!= $value2`

echo $result1
echo $result2
echo $result3

3.如果数字关系运算符与[]连用，建议使用下面的方式比较
-eq == equal
-ne ！= not equal
-gt > greater than
-lt < less than
-ge >=
-le <=

13.if语句的使用

（1）

if [ 条件 ]
   then
        语句1
  fi

（2）

if [ 条件 ]
then
       语句1
else
       语句2
fi

（3）

if[ 条件 ]
then
        语句1
elif[ 条件 ]
        语句2
else
        语句3
fi

****注意：
1.如果有else，else只能放在最后
2.if语句是可以嵌套的（建议最多3次）****
（4）
逻辑运算符 && 、|| 、

echo "please input num :"
read num
if [ `expr $num % 3` -eq 0 ] && [ `expr $num % 5` -eq 0 ]
then
    echo "3,5 YES"
else
    echo "NO"
fi

14.${},$(),$(())的区别

15.let命令

1.计算整数
2.除了可以运算+ - * / % ，还可以运算+= ，-=，/= ,*=,%=

let num2+=num1 #num2=num2+num1
let num2=num1-- #num2=num1,num1=num1-1

16 作业

• 手动键入3个数，求最大值，并输出

printf "input num1: "
read num1
printf "input num2: "
read num2
printf "input num3: "
read num3
if [ $num1 -ge $num2 ]
then 
    if [ $num1 -ge $num3 ]
    then
        printf "max=%d\n" "$num1"
    else
        printf "max=%d\n" "$num3"
    fi
elif [ $num2 -ge $num3 ]
then
    printf "max=%d\n" "$num2"
else
    printf "max=%d\n" "$num3"
fi

printf "input 3 nums: "
read num1
read num2
read num3
if ((num1>num2))
then
    if ((num1>num3))
    then
        echo "max=$num1"
    else
        echo "max=$num3"
    fi
else
    if ((num2>num3))
    then
        echo "max=$num2"
    else
        echo "max=$num3"
    fi
fi

• 手动键入2个数，并输入运算符，根据运算符+ - / *的符号给出相应计算的 结果

printf  "input num1: "
read num1
printf "yun suan: "
read ch
printf "input num2:"
read num2
ch1="+"
ch2="-"
ch3="*"
ch4="/"
if [ "$ch" == "$ch1" ]
then
    man=`expr $num1 + $sum2`
elif [ "$ch" == "$ch2" ]
then
    man=`expr $num1 - $num2`
elif [ "$ch" == "$ch3" ]
then
    man=`expr $num1 \* $sum2`
elif [ "$ch" == "$ch4" ]
then
    man=`expr $num1 / $sum2`

fi
echo $man

• 判断输入的数是否是偶数

printf "input num1: "
read num
if [ `expr $num % 2` -eq 0 ]
then
    printf "YES\n"
else
    printf "NO\n"
fi

• 创建当天文件夹

year=`date +%Y`
month=`date +%m`
day=`date +%m%d`
if [ $# == 0 ]
then
    if [ -e ~/myshell/$year/$month/$day ]
    then
        printf "%s Folder already exists\n" $day
    else
        mkdir -p ~/myshell/$year/$month/$day
        printf "%s Folder creation cuccess\n" $day
    fi
elif [ $# == 1 ]
then
    case $1 in
    "-y")
        if [ -e ~/myshell/$year ]
        then
            printf "%s Folder already exists\n" $year
        else
            mkdir -p ~/myshell/$year
            printf "%s Folder creation cuccess\n" $year
        fi
    ;;
    "-m")
        if [ -e ~/myshell/$year/$month ]
        then
            printf "%s Folder already exists\n" $month
        else
            mkdir -p ~/myshell/$year/$month
            printf "%s Folder creation success\n" $month
        fi
    ;;
    "-d")
        if [ -e ~/myshell/$year/$month/$dah ]
        then
            printf "%s Folder already exists\n" $day
        else
            mkdir -p ~/myshell/$year/$month/$day
            printf "%s Folder creation success\n" $day
        fi
    ;;
    *)
        printf "parameter error\n"
        ;;
        esac
else
    printf "parameter\n"
fi

然后 sudo cp myfile /bin/
万年历