10 個實戰及面試經常使用 Shell 腳本編寫

時間 2019-11-06

標籤實戰面試經常使用 shell 腳本編寫欄目快樂工作简体版

原文原文鏈接

注意事項mysql

1）開頭加解釋器：#!/bin/bash面試

2）語法縮進，使用四個空格；多加註釋說明。sql

3）命名建議規則：變量名大寫、局部變量小寫，函數名小寫，名字體現出實際做用。數組

4）默認變量是全局的，在函數中變量local指定爲局部變量，避免污染其餘做用域。bash

5）有兩個命令能幫助我調試腳本：set -e 遇到執行非0時退出腳本，set-x 打印執行過程。dom

6）寫腳本必定先測試再到生產上。ssh

1. 獲取隨機字符串或數字

獲取隨機8位字符串：

方法1：
# echo $RANDOM |md5sum |cut -c 1-8
471b94f2
方法2：
# openssl rand -base64 4
vg3BEg==
方法3：
# cat /proc/sys/kernel/random/uuid |cut -c 1-8
ed9e032c
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獲取隨機8位數字：

方法1：
# echo $RANDOM |cksum |cut -c 1-8
23648321
方法2：
# openssl rand -base64 4 |cksum |cut -c 1-8
38571131
方法3：
# date +%N |cut -c 1-8
69024815複製代碼

cksum：打印CRC效驗和統計字節curl

2.定義一個顏色輸出字符串函數

方法1：
function echo_color() {
    if [ $1 == "green" ]; then
        echo -e "\033[32;40m$2\033[0m"
    elif [ $1 == "red" ]; then
        echo -e "\033[31;40m$2\033[0m"
    fi
}
方法2：
function echo_color() {
    case $1 in
        green)
            echo -e "\033[32;40m$2\033[0m"
            ;;
        red)
            echo -e "\033[31;40m$2\033[0m" 
            ;;
        *) 
            echo "Example: echo_color red string"
    esac
}
使用方法：echo_color green "test"複製代碼

function關鍵字定義一個函數，可加或不加。ide

3. 批量建立用戶

#!/bin/bash
DATE=$(date +%F_%T)
USER_FILE=user.txt
echo_color(){
    if [ $1 == "green" ]; then
        echo -e "\033[32;40m$2\033[0m"
    elif [ $1 == "red" ]; then
        echo -e "\033[31;40m$2\033[0m"
    fi
}
# 若是用戶文件存在而且大小大於0就備份
if [ -s $USER_FILE ]; then
    mv $USER_FILE ${USER_FILE}-${DATE}.bak
    echo_color green "$USER_FILE exist, rename ${USER_FILE}-${DATE}.bak"
fi
echo -e "User\tPassword" >> $USER_FILE
echo "----------------" >> $USER_FILE
for USER in user{1..10}; do
    if ! id $USER &>/dev/null; then
        PASS=$(echo $RANDOM |md5sum |cut -c 1-8)
        useradd $USER
        echo $PASS |passwd --stdin $USER &>/dev/null
        echo -e "$USER\t$PASS" >> $USER_FILE
        echo "$USER User create successful."
    else
        echo_color red "$USER User already exists!"
    fi
done
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4. 檢查軟件包是否安裝

#!/bin/bash
if rpm -q sysstat &>/dev/null; then
    echo "sysstat is already installed."
else
    echo "sysstat is not installed!"
fi
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5. 檢查服務狀態

#!/bin/bash
PORT_C=$(ss -anu |grep -c 123)
PS_C=$(ps -ef |grep ntpd |grep -vc grep)
if [ $PORT_C -eq 0 -o $PS_C -eq 0 ]; then
    echo "內容" | mail -s "主題" dst@example.com
fi
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6. 檢查主機存活狀態

方法1：將錯誤IP放到數組裏面判斷是否ping失敗三次

#!/bin/bash 
IP_LIST="192.168.18.1 192.168.1.1 192.168.18.2"
for IP in $IP_LIST; do
    NUM=1
    while [ $NUM -le 3 ]; do
        if ping -c 1 $IP > /dev/null; then
            echo "$IP Ping is successful."
            break
        else
            # echo "$IP Ping is failure $NUM"
            FAIL_COUNT[$NUM]=$IP
            let NUM++
        fi
    done
    if [ ${#FAIL_COUNT[*]} -eq 3 ];then
        echo "${FAIL_COUNT[1]} Ping is failure!"
        unset FAIL_COUNT[*]
    fi
done
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方法2：將錯誤次數放到FAIL_COUNT變量裏面判斷是否ping失敗三次

#!/bin/bash 
IP_LIST="192.168.18.1 192.168.1.1 192.168.18.2"
for IP in $IP_LIST; do
    FAIL_COUNT=0
    for ((i=1;i<=3;i++)); do
        if ping -c 1 $IP >/dev/null; then
            echo "$IP Ping is successful."
            break
        else
            # echo "$IP Ping is failure $i"
            let FAIL_COUNT++
        fi
    done
    if [ $FAIL_COUNT -eq 3 ]; then
        echo "$IP Ping is failure!"
    fi
done
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方法3：利用for循環將ping通就跳出循環繼續，若是不跳出就會走到打印ping失敗

#!/bin/bash
ping_success_status() {
    if ping -c 1 $IP >/dev/null; then
        echo "$IP Ping is successful."
        continue
    fi
}
IP_LIST="192.168.18.1 192.168.1.1 192.168.18.2"
for IP in $IP_LIST; do
    ping_success_status
    ping_success_status
    ping_success_status
    echo "$IP Ping is failure!"
done
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7. 監控CPU、內存和硬盤利用率

1）CPU

藉助vmstat工具來分析CPU統計信息。函數

#!/bin/bash
DATE=$(date +%F" "%H:%M)
IP=$(ifconfig eth0 |awk -F '[ :]+' '/inet addr/{print $4}')  # 只支持CentOS6
MAIL="example@mail.com"
if ! which vmstat &>/dev/null; then
    echo "vmstat command no found, Please install procps package." 
    exit 1
fi
US=$(vmstat |awk 'NR==3{print $13}')
SY=$(vmstat |awk 'NR==3{print $14}')
IDLE=$(vmstat |awk 'NR==3{print $15}')
WAIT=$(vmstat |awk 'NR==3{print $16}')
USE=$(($US+$SY))
if [ $USE -ge 50 ]; then
    echo " Date: $DATE Host: $IP Problem: CPU utilization $USE " | mail -s "CPU Monitor" $MAIL
fi
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2）內存

#!/bin/bash
DATE=$(date +%F" "%H:%M)
IP=$(ifconfig eth0 |awk -F '[ :]+' '/inet addr/{print $4}')  
MAIL="example@mail.com"
TOTAL=$(free -m |awk '/Mem/{print $2}')
USE=$(free -m |awk '/Mem/{print $3-$6-$7}')
FREE=$(($TOTAL-$USE))
# 內存小於1G發送報警郵件
if [ $FREE -lt 1024 ]; then
    echo " Date: $DATE Host: $IP Problem: Total=$TOTAL,Use=$USE,Free=$FREE " | mail -s "Memory Monitor" $MAIL
fi
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3）硬盤

#!/bin/bash
DATE=$(date +%F" "%H:%M)
IP=$(ifconfig eth0 |awk -F '[ :]+' '/inet addr/{print $4}')  
MAIL="example@mail.com"
TOTAL=$(fdisk -l |awk -F'[: ]+' 'BEGIN{OFS="="}/^Disk \/dev/{printf "%s=%sG,",$2,$3}')
PART_USE=$(df -h |awk 'BEGIN{OFS="="}/^\/dev/{print $1,int($5),$6}')
for i in $PART_USE; do
    PART=$(echo $i |cut -d"=" -f1)
    USE=$(echo $i |cut -d"=" -f2)
    MOUNT=$(echo $i |cut -d"=" -f3)
    if [ $USE -gt 80 ]; then
        echo " Date: $DATE Host: $IP Total: $TOTAL Problem: $PART=$USE($MOUNT) " | mail -s "Disk Monitor" $MAIL
    fi
done
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8. 批量主機磁盤利用率監控

前提監控端和被監控端SSH免交互登陸或者密鑰登陸。

寫一個配置文件保存被監控主機SSH鏈接信息，文件內容格式：IP User Port

#!/bin/bash
HOST_INFO=host.info
for IP in $(awk '/^[^#]/{print $1}' $HOST_INFO); do
    USER=$(awk -v ip=$IP 'ip==$1{print $2}' $HOST_INFO)
    PORT=$(awk -v ip=$IP 'ip==$1{print $3}' $HOST_INFO)
    TMP_FILE=/tmp/disk.tmp
    ssh -p $PORT $USER@$IP 'df -h' > $TMP_FILE
    USE_RATE_LIST=$(awk 'BEGIN{OFS="="}/^\/dev/{print $1,int($5)}' $TMP_FILE)
    for USE_RATE in $USE_RATE_LIST; do
        PART_NAME=${USE_RATE%=*}
        USE_RATE=${USE_RATE#*=}
        if [ $USE_RATE -ge 80 ]; then
            echo "Warning: $PART_NAME Partition usage $USE_RATE%!"
        fi
    done
done
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9. 檢查網站可用性

1）檢查URL可用性

方法1：
check_url() {
    HTTP_CODE=$(curl -o /dev/null --connect-timeout 3 -s -w "%{http_code}" $1)
    if [ $HTTP_CODE -ne 200 ]; then
        echo "Warning: $1 Access failure!"
    fi
}
方法2：
check_url() {
if ! wget -T 10 --tries=1 --spider $1 >/dev/null 2>&1; then  
#-T超時時間，--tries嘗試1次，--spider爬蟲模式
        echo "Warning: $1 Access failure!"
    fi
}複製代碼

使用方法：check_url www.baidu.com

2）判斷三次URL可用性

思路與上面檢查主機存活狀態同樣。

方法1：利用循環技巧，若是成功就跳出當前循環，不然執行到最後一行
#!/bin/bash 
check_url() {
    HTTP_CODE=$(curl -o /dev/null --connect-timeout 3 -s -w "%{http_code}" $1)
    if [ $HTTP_CODE -eq 200 ]; then
        continue
    fi
}
URL_LIST="www.baidu.com www.agasgf.com"
for URL in $URL_LIST; do
    check_url $URL
    check_url $URL
    check_url $URL
    echo "Warning: $URL Access failure!"
done
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方法2：錯誤次數保存到變量
#!/bin/bash 
URL_LIST="www.baidu.com www.agasgf.com"
for URL in $URL_LIST; do
    FAIL_COUNT=0
    for ((i=1;i<=3;i++)); do
        HTTP_CODE=$(curl -o /dev/null --connect-timeout 3 -s -w "%{http_code}" $URL)
        if [ $HTTP_CODE -ne 200 ]; then
            let FAIL_COUNT++
        else
            break
        fi
    done
    if [ $FAIL_COUNT -eq 3 ]; then
        echo "Warning: $URL Access failure!"
    fi
done
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方法3：錯誤次數保存到數組
#!/bin/bash 
URL_LIST="www.baidu.com www.agasgf.com"
for URL in $URL_LIST; do
    NUM=1
    while [ $NUM -le 3 ]; do
        HTTP_CODE=$(curl -o /dev/null --connect-timeout 3 -s -w "%{http_code}" $URL)
        if [ $HTTP_CODE -ne 200 ]; then
            FAIL_COUNT[$NUM]=$IP  #建立數組，以$NUM下標，$IP元素
            let NUM++
        else
            break
        fi
    done
    if [ ${#FAIL_COUNT[*]} -eq 3 ]; then
        echo "Warning: $URL Access failure!"
        unset FAIL_COUNT[*]    #清空數組
    fi
done
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10. 檢查MySQL主從同步狀態

#!/bin/bash 
USER=bak
PASSWD=123456
IO_SQL_STATUS=$(mysql -u$USER -p$PASSWD -e 'show slave status\G' |awk -F: '/Slave_.*_Running/{gsub(": ",":");print $0}')  #gsub去除冒號後面的空格
for i in $IO_SQL_STATUS; do
    THREAD_STATUS_NAME=${i%:*}
    THREAD_STATUS=${i#*:}
    if [ "$THREAD_STATUS" != "Yes" ]; then
        echo "Error: MySQL Master-Slave $THREAD_STATUS_NAME status is $THREAD_STATUS!"
    fi
done
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