34 Essential Linux Bash Scripts Every Sysadmin Should Know

As a Linux engineer, well‑written scripts can greatly improve efficiency and free up time for other tasks. Below is a curated list of useful Bash scripts covering a wide range of system‑administration scenarios.

1. User Guess Number Game

#!/bin/bash
# Generate a random number between 1 and 100 and let the user guess it
num=$[RANDOM%100+1]
while :
do
  read -p "Computer generated a number between 1‑100, you guess: " cai
  if [ $cai -eq $num ]; then
    echo "Congratulations, you guessed correctly"
    exit
  elif [ $cai -gt $num ]; then
    echo "Oops, too high"
  else
    echo "Oops, too low"
  fi
done

2. Count Remote IP Connections

#!/bin/bash
# Show how many remote IPs are connected to the host (ssh, web, ftp, etc.)
netstat -atn | awk '{print $5}' | awk '{print $1}' | sort -nr | uniq -c

3. Hello World Function

#!/bin/bash
function example {
  echo "Hello world!"
}
example

4. Print Tomcat PID

#!/bin/sh
v1="Hello"
v2="world"
v3=${v1}${v2}
echo $v3
pidlist=`ps -ef|grep apache-tomcat-7.0.75|grep -v "grep"|awk '{print $2}'`
echo "tomcat Id list :$pidlist"

5. Rock‑Paper‑Scissors Game

#!/bin/bash
game=(石头 剪刀 布)
num=$[RANDOM%3]
computer=${game[$num]}
# ... (prompt user and determine win/lose)

6. Multiplication Table

#!/bin/bash
for i in `seq 9`
do
  for j in `seq $i`
  do
    echo -n "$j*$i=$[i*j] "
  done
  echo
 done

7. Install Memcached from Source

#!/bin/bash
# One‑click deployment of memcached
wget http://www.memcached.org/files/memcached-1.5.1.tar.gz
yum -y install gcc
tar -xf memcached-1.5.1.tar.gz
cd memcached-1.5.1
./configure
make
make install

8. Check If Current User Is Root

#!/bin/bash
if [ $USER == "root" ]
then
  yum -y install vsftpd
else
  echo "You are not an administrator, cannot install software"
fi

9. Simple If‑Expression Demo

#!/bin/bash -xv
if [ $1 -eq 2 ]; then
  echo "wo ai wenmin"
elif [ $1 -eq 3 ]; then
  echo "wo ai wenxing"
elif [ $1 -eq 4 ]; then
  echo "wo de xin"
elif [ $1 -eq 5 ]; then
  echo "wo de ai"
fi

10. Kill and Restart Tomcat

#!/bin/bash
pidlist=`ps -ef|grep apache-tomcat-7.0.75|grep -v "grep"|awk '{print $2}'`
echo "tomcat Id list :$pidlist"
kill -9 $pidlist
echo "KILL $pidlist:"
# restart
cd /opt/apache-tomcat-7.0.75
rm -rf work/*
cd bin
./startup.sh

11. Print Chessboard

#!/bin/bash
for i in {1..8}
do
  for j in {1..8}
  do
    sum=$[i+j]
    if [ $[sum%2] -eq 0 ]; then
      echo -ne "\033[46m  \033[0m"
    else
      echo -ne "\033[47m  \033[0m"
    fi
  done
  echo
 done

12. Count Login‑Capable Accounts

#!/bin/bash
# Method 1
grep "bash$" /etc/passwd | wc -l
# Method 2
awk -F: '/bash$/{x++}END{print x}' /etc/passwd

13. Backup MySQL Table Data

#!/bin/sh
source /etc/profile
dbName=mysql
tableName=db
mysql -uroot -proot -P3306 $dbName -e "LOAD DATA LOCAL INFILE '# /home/wenmin/wenxing.txt' INTO TABLE $tableName FIELDS TERMINATED BY ';'"

14. Real‑Time eth0 Traffic Monitor

#!/bin/bash
while :
do
  echo 'Local interface ens33 traffic:'
  ifconfig ens33 | grep "RX pack" | awk '{print $5}'
  ifconfig ens33 | grep "TX pack" | awk '{print $5}'
  sleep 1
done

15. Scan 192.168.4.0/24 Host Status

#!/bin/bash
for i in {1..254}
do
  ping -c 2 -i 0.3 -W 1 192.168.1.$i &>/dev/null
  if [ $? -eq 0 ]; then
    echo "192.168.1.$i is up"
  else
    echo "192.168.1.$i is down"
  fi
done

16. Create User with Password Prompt

#!/bin/bash
read -p "Enter username: " user
if [ -z $user ]; then
  echo "You must provide a username"
  exit 2
fi
stty -echo
read -p "Enter password: " pass
stty echo
pass=${pass:-123456}
useradd "$user"
echo "$pass" | passwd --stdin "$user"

17. Sort Three Integers

#!/bin/bash
read -p "Enter first integer: " num1
read -p "Enter second integer: " num2
read -p "Enter third integer: " num3
# Simple bubble‑sort logic
if [ $num1 -gt $num2 ]; then tmp=$num1; num1=$num2; num2=$tmp; fi
if [ $num1 -gt $num3 ]; then tmp=$num1; num1=$num3; num3=$tmp; fi
if [ $num2 -gt $num3 ]; then tmp=$num2; num2=$num3; num3=$tmp; fi
echo "Sorted numbers: $num1,$num2,$num3"

18. Time‑Based Greeting Script

#!/bin/bash
tm=$(date +%H)
if [ $tm -le 12 ]; then
  msg="Good Morning $USER"
elif [ $tm -gt 12 -a $tm -le 18 ]; then
  msg="Good Afternoon $USER"
else
  msg="Good Night $USER"
fi
echo "Current time: $(date +"%Y-%m-%d %H:%M:%S")"
echo -e "\033[34m$msg\033[0m"

19. Write Text to File

#!/bin/bash
cd /home/wenmin/
touch wenxing.txt
echo "I lov cls" >> wenxing.txt

20. Sum Numbers with For Loop

#!/bin/bash
s=0
for ((i=1;i<100;i++))
do
  s=$[s+i]
 done
echo $s
# Additional loops omitted for brevity

21. Iterate Over Arguments

#!/bin/bash
for i "$*"
do
  echo "wenmin xihuan $i"
done
for j "$@"
do
  echo "wenmin xihuan $j"
done

22. Weekly Log Backup with tar

#!/bin/bash
# Run every Friday via cron
tar -czf log-`date +%Y%m%d`.tar.gz /var/log

23. Sum and Division Functions

#!/bin/bash
function sum {
  s=$[ $1 + $2 ]
  echo $s
}
read -p "input your parameter " p1
read -p "input your parameter " p2
sum $p1 $p2
function multi {
  r=$[ $1 / $2 ]
  echo $r
}
read -p "input your parameter " x1
read -p "input your parameter " x2
multi $x1 $x2
let v3=$v1+$v2
echo $v3

24. Case‑Statement Demo

#!/bin/bash
case $1 in
 1) echo "wenmin" ;;
 2) echo "wenxing" ;;
 3) echo "wemchang" ;;
 4) echo "yijun" ;;
 5) echo "sinian" ;;
 6) echo "sikeng" ;;
 7) echo "yanna" ;;
 *) echo "danlian" ;;
esac

25. Tomcat Auto‑Monitor and Restart

#!/bin/sh
TomcatID=$(ps -ef|grep tomcat|grep -w 'apache-tomcat-7.0.75'|grep -v 'grep'|awk '{print $2}')
StartTomcat=/opt/apache-tomcat-7.0.75/bin/startup.sh
WebUrl=http://192.168.254.118:8080/
GetPageInfo=/dev/null
TomcatMonitorLog=/tmp/TomcatMonitor.log
Monitor(){
  echo "[info] Starting Tomcat monitor...$(date '+%F %H:%M:%S')"
  if [ $TomcatID ]; then
    echo "[info] Tomcat PID: $TomcatID"
    TomcatServiceCode=$(curl -s -o $GetPageInfo -m 10 --connect-timeout 10 $WebUrl -w %{http_code})
    if [ $TomcatServiceCode -eq 200 ]; then
      echo "[info] Tomcat responded with 200, service OK"
    else
      echo "[error] Tomcat error $TomcatServiceCode, restarting..."
      kill -9 $TomcatID
      sleep 3
      $StartTomcat
    fi
  else
    echo "[error] Tomcat process not found, starting..."
    $StartTomcat
  fi
  echo "------------------------------"
}
Monitor >> $TomcatMonitorLog

26. Create Linux Account via Positional Parameters

#!/bin/bash
useradd "$1"
echo "$2" | passwd --stdin "$1"

27. Show Passed Arguments

#!/bin/bash
echo "$0 $1 $2 $3"
echo $#
echo $@
echo $*

28. Memory and Disk Alert Script

#!/bin/bash
disk_size=$(df / | awk '/\//{print $4}')
mem_size=$(free | awk '/Mem/{print $4}')
while :
do
  if [ $disk_size -le 512000 -a $mem_size -le 1024000 ]; then
    mail -s "Warning" root <<EOF
Insufficient resources, 资源不足
EOF
  fi
done

29. Check If File Exists

#!/bin/bash
if [ -f /home/wenmin/datas ]; then
  echo "File exists"
fi

30. While Loop Sum Example

#!/bin/bash
s=0
i=1
while [ $i -le 100 ]
do
  s=$[s+i]
  i=$[i+1]
 done
echo $s
echo $i

31. One‑Click LNMP (RPM) Deployment

#!/bin/bash
# Install LAMP stack on CentOS/RHEL 7
yum -y install httpd
yum -y install mariadb mariadb-devel mariadb-server
yum -y install php php-mysql
systemctl start httpd mariadb
systemctl enable httpd mariadb

32. Read Console Parameters with Timeout

#!/bin/bash
read -t 7 -p "input your name " NAME
echo $NAME
read -t 11 -p "input you age " AGE
echo $AGE
read -t 15 -p "input your friend " FRIEND
echo $FRIEND
read -t 16 -p "input your love " LOVE
echo $LOVE

33. Simple Copy Script

#!/bin/bash
cp $1 $2

34. File Existence Check

#!/bin/bash
if [ -f file.txt ]; then
  echo "文件存在"
else
  echo "文件不存在"
fi

The collection demonstrates how Bash can be leveraged for everyday Linux system tasks, offering ready‑to‑use snippets that can be adapted or extended for production environments.