The 12th Chapter shell script Writing and common face question (i.)

Precautions

1) Opening add interpreter: #!/bin/bash

2) syntax indentation, use four spaces, and more explanatory notes.

3) Naming recommendation rules: variable name capital, local variable lowercase, function name lowercase, the name reflects the actual role.

4) The default variable is global, and in the function the local variable is specified as a locally variable to avoid contaminating other scopes.

5) There are two commands that can help me debug the script: Set-e encounters a non-0 o'clock exit script, set-x the print execution process.

6) Write scripts must be tested before production.

12.1 getting a random string or number

Get a random 8-bit string:

Method 1:# echo $RANDOM |md5sum |cut-c 1-8471b94f2 method 2:# OpenSSL rand-base64 4vg3beg== method 3:# Cat/proc/sys/kernel/random/uuid | Cut-c 1-8ed9e032c

Get a random 8-digit number:

Method 1:# echo $RANDOM |cksum |cut-c 1-823648321 method 2:# OpenSSL rand-base64 4 |cksum |cut-c 1-838571131 method 3:# Date +%n |cut-c 1-869024815

Cksum: Print CRC validation and statistics bytes

12.2 Defining a color output string function

Method 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} Method 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} How to use:echo_color green " Test

The Functions keyword defines a function that can be added or not added.

12.3 Creating users in batches

#!/bin/bashdate=$ (date +%f_%t) User_file=user.txtecho_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}#  If the user file exists and the size is greater than 0, backup if [ -s  $USER _file ]; then    mv  $USER _ file ${user_file}-${date}.bak    echo_color green  "$USER _file exist,  rename ${user_file}-${date}.bak "fiecho -e " User\tpassword " >>  $USER _ fileecho  "----------------"  >>  $USER _filefor 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! "     fidone

12.4 Check if the package is installed

#!/bin/bashif rpm-q Sysstat &>/dev/null; Then echo "Sysstat is already installed." else echo "Sysstat is not installed!" Fi

12.5 checking Service status

#!/bin/bashport_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 "Content" | Mail-s "Theme" [Email Protected]fi

12.6 Checking host survival status

Method 1: put the error IP into the array to determine if the ping failed three times

#!/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[*]    fidone

method 2: Put the number of errors in the Fail_count variable to determine if the ping failed three times

#!/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!"     fidone

Method 3: use the For loop to ping the loop to continue, and if you do not jump, you will go to the print ping failure

#!/bin/bashping_success_status () {if ping-c 1 $IP >/dev/null; then echoes "$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

12.7 monitoring CPU, memory, and hard disk utilization

1) CPU

Use the Vmstat tool to analyze CPU statistics.

#!/bin/bashdate=$ (date +%f " "%h:%m) ip=$ (ifconfig eth0 |awk -f  ' [ :]+ '   '/inet addr/{print $4} '   #  only supports centos6mail= "[email protected]" if !  which vmstat &>/dev/null; then    echo  "Vmstat command  no found, please install procps package. "      exit 1fius=$ (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"   $MAILFI

2) Memory

#!/bin/bashdate=$ (Date +%f ""%h:%m) ip=$ (ifconfig eth0 |awk-f ' [:]+ '/inet addr/{print $4} ') mail= "[email protected]" to tal=$ (free-m |awk '/mem/{print $} ') use=$ (free-m |awk '/mem/{print $3-$6-$7} ') free=$ (($TOTAL-$USE)) # Memory less than 1G send alert mail if [$ FREE-LT 1024]; Then echo "Date: $DATE Host: $IP problem:total= $TOTAL, use= $USE, free= $FREE" | Mail-s "Memory Monitor" $MAILfi

3) Hard Drive

#!/bin/bashdate=$ (date +%f " "%h:%m) ip=$ (ifconfig eth0 |awk -f  ' [ :]+ '   '/inet addr/{print $4} ')   mail= "[email protected]" total=$ (Fdisk -l |awk  -f ' [:  ]+ '   ' begin{ofs= ' = '}/^disk \/dev/{printf  '%s=%sg, ', $2,$3} ') part_use=$ (df - h |awk  ' begin{ofs= "="}/^\/dev/{print $1,int ($), $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     fidone

12.8 Bulk host disk utilization monitoring

The prerequisite monitoring side and the monitored side SSH free interactive login or key login.

Write a configuration file to save the monitored host SSH connection information, file content format: IP User Port

#!/bin/bashhost_info=host.infofor 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  [email  Protected] $IP   ' df -h '  >  $TMP _file    use_rate_list=$ (awk  ' begin{ofs= "="}/^\/dev/{print $1,int ($)} '   $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&nBSP; " warning:  $PART _name partition usage  $USE _rate%! "         fi    donedone

12.9 Checking the availability of sites

1) Check URL availability

Method 1:check_url () {http_code=$ (Curl-o/dev/null--connect-timeout 3-s-w "%{http_code}" $) if [$HTTP _code-ne 200 ];    Then echo "Warning: Access failure!" Fi} Method 2:check_url () {if! wget-t--tries=1--spider >/dev/null 2>&1; then #-t time Out,--tries try 1 times,--spider crawler    echo "Warning: Access failure!" FI} How to use: Check_url www.baidu.com

2) determine three times URL availability

The idea is the same as above to check the host's survival status.

Method 1: Take advantage of the looping technique, if successful, jump out of the current loop, otherwise execute to the last line #!/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 Method 2: The number of errors saved to the variable #!/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! "     fidone Method 3: Number of errors saved to array #!/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    #创建数组, with $num subscript, $IP elements             let NUM++         else            break         fi    done    if  [ ${#FAIL_COUNT [*]} -eq 3 ]; then        echo   "warning:  $URL  access failure!"         unset FAIL_COUNT[*]     #清空数组      fidone

This chapter is written in shell script examples are more practical, in the interview also often appear, I hope you refer to the more hands-on writing, do not copy and paste to take to run, this is not learning! If you have any questions, please dabigatran Exchange:323779636 (Shell/python devops Development Group)

This article is from the "Li Zhenliang Technology Blog" blog, make sure to keep this source http://lizhenliang.blog.51cto.com/7876557/1929044

The 12th Chapter shell script Writing and common face question (i.)