脚本案例（二）

1.数据库备份

• 将数据库备份到/mnt/mysqldump
• 当备份文件存在时询问
• 选择 S)跳过    B)备份    O)跳过

[root@141 MY_SHELL]# cat dbdump.sh 
#!/bin/bash
DB_MESSAGE=`mysql -uroot -EN -e "show databases;"| grep -E "^\*|schema$ -v"`
####规则显示数据库名
mkdir -p /mnt/mysqldump   ##新建备份目录
for DB_NAME in ${DB_MESSAGE}
do
    if 
    [ -e "/mnt/mysqldump/${DB_NAME}.mysql" ]
##检测数据库备份文件是否存在
    then
        echo "${DB_NAME}.mysql exists" 
        read -p "INSTRUCTION: " p
    case $p in    
        s)     ##用户选择跳过
            echo skip~~~
            exit 0
        ;;
        o)  ##覆盖数据库文件
            mysqldump -uroot ${DB_MESSAGE}> /mnt/mysqldump/${DB_NAME}.sql
            echo Overwrite
        ;;
        b)  ##备份文件
            mysqldump -uroot $DB_MESSAGE > /mnt/mysqldump/${DB_NAME}.sql
            echo backup
        ;;
        *)       ##其余显示错误
            echo error
        ;;
    esac
    else          ##其余情况均直接备份
        mysqldump -uroot $DB_MESSAGE > /mnt/mysqldump/${DB_NAME}.sql
    [ "$?" -eq "0" ]&&{
        echo "$DB_NAME is backped"
    }
    fi
done

2.时钟时秒倒计时

[root@141 mnt]# cat TIMER.sh 
#!/bin/bash
for NUM in {0..9}
do
    echo "$((10 - $NUM))"
    sleep 1
done

设定从1：10开始倒计时，计时结束后输出提示并结束。

[root@141 ~]# cat timer.sh 
#!/bin/bash:
MIN=1               #赋初值
for ((SEC=10;SEC>=0;SEC--))
do
while [ "$SEC" -eq "0" ]    #设定SEC=0-->59
do
    echo -ne "\r$MIN:$SEC\r"   #输出时间并清屏
    if 
    [ "$MIN" -eq "0" ]
    then
        echo finished
        exit 0
    else    
        sleep 1 
        echo -ne "\r$MIN:$SEC\r"
        SEC=59
        MIN=$(($MIN-1))
    fi
        break
done
    echo -n "$MIN:$SEC "
        sleep 1       #休眠1s
    echo -ne "\r    \r"
done

检验成功

[root@141 ~]# sh timer.sh 
0:55 

[root@141 ~]# sh timer.sh 
finished

倒计时完整精简版

#!/bin/bash
read -p "Hour:" h
read -p "Minute:" m
read -p "Second:" s
p=$[h*3600+m*60+s]
for ((i=$p;i>0;i--))
do
        H=$[$i/3600]
        M=$[$i/60%60]
        S=$[$i%60]
        echo -ne "\r$H:$M:$S\r"
        sleep 1
done

3.计算器

[root@141 mnt]# cat Calculator.sh 
#!/bin/bash

Continue(){
read -p "Continue...?y/n" CMD
case $CMD in
    y)
    Cal
    ;;
    n)
    exit 0
    ;;
    *)
    Continue
    ;;
esac
}
Cal(){
read -p "Number:" a
read -p "Number:" b
read -p "Operation:" OPR
case $OPR in
    +)
    echo  $(($a+$b))
    ;;
    -)
    echo  $(($a-$b))
    ;;
    *)
    echo  $(($a*$b))
    ;;
    /)
    echo  $(($a/$b))
    ;;
    %)
    echo  $(($a%$b))
    ;;
    *)
    error
    ;;
esac
Continue
}
Cal

4.批量添加用户

#!/bin/bash
check_file(){
    if
    [ "$#" -ne "2" ]
    then
        echo "File does not match"
        exit 0
    elif
    [ ! -e "$2" ]||[ ! -e "$1" ]
    then
        echo "File does not exist"
        exit 0
    fi
}
check_line(){
        USER_LINE=`awk 'BEGIN{N=0}{N++}END{print N}' $1`
        PASS_LINE=`awk 'BEGIN{N=0}{N++}END{print N}' $2`
    if
    [ "$USER_LINE" -ne "$PASS_LINE" ]
    then
        echo ERROR_LINE
        exit 0
    fi
}
useradd(){
        PASSLINE=`awk 'BEGIN{N=0}{N++}END{print N}' $2`
    for LINE_NUM in `seq 1 $PASSLINE`
    do
        USERNAME=`sed -n "${LINE_NUM}p" $2`
        PASSWORD=`sed -n "${LINE_NUM}p" $3`
        useradd $USERNAME
    [ "$?" -eq "0" ]&&{
        echo $PASSWORD | passwd --stdin $USERNAME&>/dev/null && echo $USERNAME exists

}
    done
}
case $1 in
    add)
    check_file $2 $3
    check_line $3 $3
    useradd $2
    ;;
    *)
    ;;
esac

5.判断文件存在或输出文件属性

#!/bin/bash
if 
    [ "$#" -ne "1" ]
    then
        echo ERROR
fi
for i in f b L d S
do
    if
    [ -"$i" "$1" ]
    then    
    case $i in 
        f)
        echo "$1 exists and is a regular file"
        ;;
        b)
        echo "$1 exists and is block special"
        ;;
        L)
        echo "$1 exists and is a symbolic link"
        ;;
        d)
        echo "$1 exists and is a directory"
        ;;
        S)
        echo "$1 exists and is a socket"
        ;;
    esac
    fi
done

检验：

[root@141 mnt]# sh checkfile.sh /mnt/
/mnt/ exists and is a directory
[root@141 mnt]# sh checkfile.sh /dev/vda
/dev/vda exists and is block special
[root@141 mnt]# sh checkfile.sh /etc/system-release
/etc/system-release exists and is a regular file
/etc/system-release exists and is a symbolic link

6.检测可以连接的主机，并使用ssh连接获取hostname

function testIp {
        for((i=$1;i<=$2;i++))
        do
        ip=$3.$i
        ping -c1 -w1 $ip &>/dev/null
        #ping网段内主机，根据命令执行返回值来确定下一步的动作
        if [ $? -eq 0 ]
        then
                result=`/root/useradd/answer.exp $ip redhat hostname | grep foundation | cut -d . -f 1-3`
                #执行自动应答脚本根据命令执行结果处理输出
                echo $result | grep foundation &>/dev/null
                if [ $? -ne 0 ]
                then
                        echo "ssh connection refused  by host $ip"
                else
                        echo "$ip's hostname is: $result"
                fi
        else
                echo "$ip can not be reached!"
        fi
        done
}
print_usage
read -p "Please input startip endip and zone: " ipstart ipend ipzone
#函数调用
testIp $ipstart $ipend $ipzone

7.单行或者多行字符反转

#!/bin/bash
for arg in $@
do
    inputstr=$arg
    len=${#inputstr}
    for((i=1;i<=$len;i++))
    do
        echo -n ${inputstr:0-$i:1}
        #字符从右切片，每次左移一位取一个字符
    done
    echo ""
done

[root@141 mnt]# sh reve.sh agdjkvklf
flkvkjdga