11.read命令

1.等待輸入的值，賦給read后面的變量

printf "請(qǐng)輸入一個(gè)數(shù)："
read num
printf "請(qǐng)?jiān)佥斎胍粋€(gè)數(shù)："
read num1
pirntf "num=%s\nnum1=%s\n" "$num"  "$num1"

12.整數(shù)基本運(yùn)算

1.算術(shù)運(yùn)算+ ，- ，* ， /， %

value1=1
value2=2
value3=`expr $value1 + $value2`
value4=`expr $value1 - $value2`
value5=`expr $value1 \* $value2`  //乘法必須這么寫
value6=`expr $value1 / $value2`
value=`expr $value1 % $value2`

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

注意：$()和``代表取出數(shù)據(jù)的結(jié)果集
2.關(guān)系運(yùn)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.如果數(shù)字關(guān)系運(yùn)算符與[]連用，建議使用下面的方式比較
-eq == equal
-ne ！= not equal
-gt > greater than
-lt < less than
-ge >=
-le <=

13.if語句的使用

（1）

if [ 條件 ]
   then
        語句1
  fi

（2）

if [ 條件 ]
then
       語句1
else
       語句2
fi

（3）

if[ 條件 ]
then
        語句1
elif[ 條件 ]
        語句2
else
        語句3
fi

****注意：
1.如果有else，else只能放在最后
2.if語句是可以嵌套的（建議最多3次）****
（4）
邏輯運(yùn)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.${},$(),$(())的區(qū)別

15.let命令

1.計(jì)算整數(shù)
2.除了可以運(yùn)算+ - * / % ，還可以運(yùn)算+= ，-=，/= ,*=,%=

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

16 作業(yè)

• 手動(dòng)鍵入3個(gè)數(shù)，求最大值，并輸出

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

• 手動(dòng)鍵入2個(gè)數(shù)，并輸入運(yùn)算符，根據(jù)運(yùn)算符+ - / *的符號(hào)給出相應(yīng)計(jì)算的 結(jié)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

• 判斷輸入的數(shù)是否是偶數(shù)

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

• 創(chuàng)建當(dāng)天文件夾

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/
萬年歷