shell 练习

1. 备份并压缩 /etc 下所有内容到 /root/bak，存放形式为 2020_2_15_etc.tar.bz2。

#!/bin/bash

DestDir=/root/bak
DateName=$(date +%Y_%m_%d)

[ "$UID" -ne 0 ] && echo "You need to be root to perform this command."  && exit

cd /etc
tar cjf ${DestDir}/${DateName}.tar.bz2 *

查看是否为root用户，用 $UID

shell 进行的cd目录不需要切换回来，因为是子进程进行的 

2. 查看内存占用率，如果大于80%则报警

#!/bin/bash

Use=$(free | awk '/^Mem/{print $3/$2*100}')
[ ${Use%.*} -gt 80 ] && echo "warning" || echo "ok"

注意只能比较整数，首先用 ${VAR%MOD}的到整数

注意整数比大小用 -gt，字符串用 >=

3. 

#!/bin/bash

string="Bash is an excellent excellent programming language language"
echo "${string}"
cat << eof
1] get the length of string     
2] delete all language
3] replace first excellent with best
4] replace all excellent with best
eof
read -p "please input [1|2|3|4] : "  var
case $var in
        1)
                echo $(echo ${string} | wc -c)
                ;;
        2)
                echo ${string//language/}
                ;;
        3)
                echo ${string/excellent/best}
                ;;
        4)
                echo ${string//excellent/best}
                ;;
        *)
                ;;
esac

 4. 查看sshd服务状态，进程是否启动，端口状态

#!/bin/bash

# 1. 判断服务状态
ssh_status=$(systemctl status sshd | awk '/^ +Active/{print $2}')
if [ "$ssh_status" == "active" ]; then
        echo "服务状态已启动..."
else
        echo "服务状态未启动..."
fi
# 2. 判断服务端口号
netstat -ntlp |grep sshd  | grep -v grep &>/dev/null
if [ $? -eq 0 ]; then
        echo "服务端口正常"
else
        echo "服务端口异常"
fi
# 3. 判断服务进程是否存在
ps -aux |grep sshd  | grep -v grep &>/dev/null
if [ $? -eq 0 ]; then
        echo "服务进程正常"
else
        echo "服务进程异常"
fi

 5. 查看系统版本

tt=$(cat /etc/red | awk '{print $(NF-1)}')

6. 实现rsync的服务脚本

#!/bin/bash

RsyncLock=/var/run/rsync.pid

source /etc/init.d/functions

case $1 in
        start)
                if [ -f ${RsyncLock} ]; then
                        action "Rsync is Running ..."   /bin/false
                else
                        touch ${RsyncLock}
                        rsync --daemon
                        action "Rsync Started ..."      /bin/true
                fi
                ;;
        stop)
                if [ -f ${RsyncLock} ]; then
                        rm ${RsyncLock}
                        killall rsync
                        action "Rsync Killed ..."       /bin/true
                else
                        action "Rsync is not Running ..."       /bin/false
                fi
                ;;
        status)
                if [ -f ${RsyncLock} ]; then
                        RsyncPid=$(ps aux |grep rsync | grep -v grep | awk '/ rsync /{print $2}')
                        echo "Rsync is Running ( $RsyncPid )"
                else
                        echo "Rsync is not Running"
                fi
                ;;
        *)
                echo "Usage : $0 [start | stop | status ]"
                ;;
esac

 7.实现nginx服务脚本

相对于上一脚本，添加了 nginx -t 的检查，和整个脚本的锁机制。

#!/bin/bash

Nginx=/usr/local/nginx/sbin/nginx
Lock=/tmp/${0}.lock

echo_result()
{
    if [ "$1" -eq 0 ]; then
        action "$2" /bin/true
    else
        action "$2" /bin/false
        rm -f ${Lock}
        exit
    fi
}

nginx_test()
{
    ${Nginx} -t &>/dev/null

    if [ "$?" -ne 0 ]; then
        read -p "nginx.conf have error, do you need to modify [y|n]? "  rc
        case "$rc" in
            y|Y|Yes|yes|YES)
                ${Nginx} -t &>/tmp/${0}.err
                ErrLine=$(cat /tmp/xxx.err | awk -F: '/:[0-9]+$/{print $NF}')
                rm /tmp/${0}.err    
                vi /usr/local/nginx/conf/nginx.conf +${ErrLine}
                ;;
            n|N|No|NO)
                ;;
            *)
                echo "input [y|n]"    
                ;;
        esac
    fi
}

source /etc/init.d/functions

if [ -f ${Lock} ]; then
    echo "command is running, please wait..."
    exit
else
    touch ${Lock}
fi

[ "$UID" -ne 0 ] && echo "you need to be root to run this command !" && exit
case "$1" in
    start)
        if [ -e /var/run/nginx.pid ]; then
            action "nginx is starting" /bin/false
        else
            nginx_test
            ${Nginx} &>/dev/null
            echo_result $? "nginx start"
            touch /var/run/nginx.pid
        fi
        ;;
    stop)
        if [ -e /var/run/nginx.pid ]; then
            nginx_test
            ${Nginx} -s stop &>/dev/null
            echo_result $? "nginx stop"
            rm -f /var/run/nginx.pid
        else
            action "nginx is not starting" /bin/false
        fi
        ;;
    reload)
        if [ -e /var/run/nginx.pid ]; then
            nginx_test
            ${Nginx} -s reload &>/dev/null
            echo_result $? "nginx reload"
        else
            action "nginx is not starting" /bin/false
        fi
        ;;
    status)
        nginx_pid=$(ps aux | grep "nginx: master" | grep -v grep | awk '{print $2}')
        if [ -z ${nginx_pid} ]; then
            action "nginx is not starting" /bin/false
        else
            action "nginx is running ( ${nginx_pid} )" /bin/true
        fi
        ;;
    *)
        echo "Usage : $0 [start | stop | reload | status]"
        ;;
esac

rm -f ${Lock}

 8. 批量创建用户

#!/bin/bash

[ $UID -ne 0 ] && echo "you must to be root to run this command !" && exit

read -p "please input name prefix :" Prefix
[ -z "${Prefix}" ] && echo "please input vaild value" && exit

read -p "please input num :" Num
if [[ ! ${Num} =~ ^[0-9]+$ ]]; then
        echo "please input integer"
        exit
fi

read -p "confirm create ${Prefix}1 ~ ${Prefix}${Num} [y|n]"  rc

case "$rc" in
        y|Y|yes|YES|Yes)
                for n in $(seq ${Num})
                do
                        Name=${Prefix}${n}
                        id ${Name} &>/dev/null
                        if [ $? -eq 1 ]; then
                                user_passwd=$(echo ${RANDOM} | md5sum | cut -c 1-6)
                                adduser ${Name}
                                echo ${user_passwd} | passwd ${Name} --stdin &>/dev/null
                                echo "${Name}   ${user_passwd}" >> /tmp/user.log
                                echo "Success to add ${Name}"
                        else
                                echo "${Name} already exists"
                        fi
                done
                ;;
        n|N|no|No|NO)
                exit
                ;;
        *)
                exit
                ;;
esac

 9. 批量删除用户

#!/bin/bash

[ $UID -ne 0 ] && echo "you must to be root to run this command !" && exit

read -p "please input name prefix :" Prefix
[ -z "${Prefix}" ] && echo "please input vaild value" && exit

read -p "please input num :" Num
if [[ ! ${Num} =~ ^[0-9]+$ ]]; then
        echo "please input integer" 
        exit
fi

read -p "confirm delete ${Prefix}1 ~ ${Prefix}${Num} [y|n] : "  rc

case "$rc" in
        y|Y|yes|YES|Yes)
                for n in $(seq ${Num})
                do
                        Name=${Prefix}${n}
                        id ${Name} &>/dev/null
                        if [ $? -eq 0 ]; then
                                userdel -r ${Name}
                                [ $? -eq 0 ] && echo "${Name} success to del" || echo "${Name} failed to del"
                        else
                                echo "${Name} not exists"
                        fi
                done
                ;;
        n|N|no|No|NO)
                exit
                ;;
        *)
                exit
                ;;
esac

 10. IP探测

#!/bin/bash

Network="192.168.1"
for n in {1..254}
do
        {
        Address="${Network}.${n}"
        ping  -c 1 -W 1 ${Address} &>/dev/null
        [ $? -eq 0 ] && echo "${Address} is alive" || echo "${Address} is down"
        } &
done
wait
echo "ip detection complete"

使用 { ... } & 的作用是，让括号内的代码成后台进程，不影响主shell进程的执行，进而实现并发执行。

wait 的作用是，等待所有进程执行完成

11. 猜数字

#!/bin/bash

random_num=$((${RANDOM}%100+1))

echo "$random_num"
while true
do
        read -p "Please input your answer, [q] to exit : " rc
        [ "${rc}" == "q" ] && exit
        if [[ ! ${rc} =~ ^[0-9]+$ ]]; then
                echo "Please input integer"
                continue
        fi

        [ "${rc}" -eq ${random_num} ] && echo "Congratulations on success !" && break

        if [ "${rc}" -gt ${random_num} ]; then
                echo "Guess big"
        else
                echo "Guess small"
        fi
        let i++
        [ $i -gt 5 ] && echo "Run out of 6 chances !" && break
done

 12. 从文本读取用户名密码，并用while创建用户，设置密码

#!/bin/bash

while read line
do
        user_name=${line%:*}
        user_passwd=${line#*:}
        id ${user_name} &>/dev/null
        if [ $? -eq 0 ]; then
                echo "${user_name} is exists"
        else
                useradd ${user_name}
                echo ${user_passwd} | passwd ${user_name} --stdin &>/dev/null
                [ $? -eq 0 ] && echo "${user_name} create succeed" || echo "${user_name} create failed" 

        fi
done <user.txt

 13. 使用关联数组，统计元素个数

#!/bin/bash

declare -A array_pass
while read line
do
        key=$(echo $line | awk -F: '{print $NF}')
        let array_pass[$key]++
done</etc/passwd

for n in ${!array_pass[@]}
do
        echo "$n : ${array_pass[$n]}"
done

关联数组需要先声明

awk '{ips[$2]++} END{for(i in ips) print i,ips[i]}' user.txt

要统计谁，谁就作为索引。