149 Practical Shell Script Examples Every Ops Engineer Should Know

For operations engineers, shell scripts can reduce repetitive work and greatly improve efficiency; mastering them is an essential skill.

Below are selected examples from the "149 Practical Shell Script Cases" collection (the full set contains 68 pages with clear indexing). Each example includes a brief description and the corresponding Bash code.

1. Find zombie processes in Linux

#!/bin/bash
# Find zombie processes
ps aux | awk '{if($8 == "Z"){print $2,$11}}'

2. Delete zero‑size files in a directory

#!/bin/bash
# Delete zero‑size files
dir="/var/www/html"
find $dir -type f -size 0 -exec rm -rf {} \;

3. Read five numbers (0‑100) and compute sum, min, and max

#!/bin/bash
COUNT=1
SUM=0
MIN=0
MAX=100
while [ $COUNT -le 5 ]; do
  read -p "Please enter an integer (0‑100): " INT
  if [[ ! $INT =~ ^[0-9]+$ ]]; then
    echo "Input must be an integer!"
    exit 1
  elif [ $INT -gt 100 ]; then
    echo "Input must be within 100!"
    exit 1
  fi
  SUM=$((SUM+INT))
  [ $MIN -lt $INT ] && MIN=$INT
  [ $MAX -gt $INT ] && MAX=$INT
  let COUNT++
done
echo "SUM: $SUM"
echo "MIN: $MIN"
echo "MAX: $MAX"

4. Print various time formats

#!/bin/bash
# Print various time formats

echo "Display abbreviated weekday (e.g., Sun)"
date +%a

echo "Display full weekday (e.g., Sunday)"
date +%A

echo "Display abbreviated month (e.g., Jan)"
date +%b

echo "Display full month (e.g., January)"
date +%B

echo "Display numeric month (e.g., 12)"
date +%m

echo "Display numeric day (e.g., 01)"
date +%d

echo "Display numeric year (e.g., 2023)"
date +%Y

echo "Display year‑month‑day"
date +%F

echo "Display hour (24‑hour)"
date +%H

echo "Display minute (00..59)"
date +%M

echo "Display second"
date +%S

echo "Display nanosecond"
date +%N

echo "Combined format"
date +"%Y%m%d %H:%M:%S"

5. Check whether a file or directory exists

#!/bin/bash
# Check existence of file or directory
if [ $# -eq 0 ]; then
  echo "No arguments provided, please specify a file or directory"
  echo "Usage: $0 [filename|dirname]"
  exit 1
fi
if [ -f "$1" ]; then
  echo "The file exists"
  ls -l "$1"
elif [ -d "$1" ]; then
  echo "The directory exists"
  ls -ld "$1"
else
  echo "The specified file or directory does not exist"
fi

6. Sort three input integers

#!/bin/bash
# Prompt user for three integers and sort them
read -p "Please enter an integer: " num1
read -p "Please enter an integer: " num2
read -p "Please enter an integer: " num3
# Ensure num1 holds the smallest value
if [ $num1 -gt $num2 ]; then
  tmp=$num1; num1=$num2; num2=$tmp
fi
if [ $num1 -gt $num3 ]; then
  tmp=$num1; num1=$num3; num3=$tmp
fi
# Ensure num2 holds the middle value
if [ $num2 -gt $num3 ]; then
  tmp=$num2; num2=$num3; num3=$tmp
fi
echo "Sorted numbers (ascending): $num1, $num2, $num3"

7. Retrieve the local MAC address

#!/bin/bash
# Retrieve local MAC address
ip a s | awk 'BEGIN{print "Local MAC address information:"}/^[0-9]/{print $2;getline;if($0~/link\/ether/){print $2}}' | grep -v lo:

8. Determine whether a given year is a leap year

#!/bin/bash
# Prompt for a year and determine if it is a leap year
read -p "Please enter a year: " year
if [ -z "$year" ]; then
  echo "No year entered"
  exit 1
fi
if [[ "$year" =~ [a-zA-Z] ]]; then
  echo "Input is not a number"
  exit 1
fi
if [ $((year % 4)) -eq 0 ] && [ $((year % 100)) -ne 0 ] || [ $((year % 400)) -eq 0 ]; then
  echo "$year is a leap year"
else
  echo "$year is not a leap year"
fi