149 Must‑Know Shell Script Examples to Boost Your Sysadmin Efficiency

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

Today we share the "149 Practical Shell Script Cases" (68 pages, clear index, searchable, copyable code) – a free resource to help you learn and practice.

Below are selected examples:

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, max

#!/bin/bash
COUNT=1
SUM=0
MIN=0
MAX=100
while [ $COUNT -le 5 ]; do
  read -p "Enter an integer (0‑100): " INT
  if [[ ! $INT =~ ^[0-9]+$ ]]; then
    echo "Input must be an integer!"
    exit 1
  elif [ $INT -gt 100 ]; then
    echo "Input must be ≤100!"
    exit 1
  fi
  SUM=$((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 time formats
echo "Weekday abbreviation (Sun):"
date +%a
echo "Weekday full name (Sunday):"
date +%A
echo "Month abbreviation (Jan):"
date +%b
echo "Month full name (January):"
date +%B
echo "Numeric month (12):"
date +%m
echo "Numeric day (01):"
date +%d
echo "Year (2023):"
date +%Y
echo "YYYY‑MM‑DD:"
date +%F
echo "Hour (24‑h):"
date +%H
echo "Minute (00‑59):"
date +%M
echo "Second:"
date +%S
echo "Nanosecond:"
date +%N
echo "Combined:"
date +"%Y%m%d %H:%M:%S"

5. Check whether a file or directory exists

#!/bin/bash
# Check existence
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 "File exists"
  ls -l "$1"
elif [ -d "$1" ]; then
  echo "Directory exists"
  ls -ld "$1"
else
  echo "No such file or directory"
fi

6. Sort three input integers

#!/bin/bash
# Prompt for three integers and sort them
read -p "Enter first integer: " num1
read -p "Enter second integer: " num2
read -p "Enter third integer: " num3
tmp=0
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 (ascending): $num1, $num2, $num3"

7. Get local MAC address

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

8. Determine leap year

#!/bin/bash
# Leap year check
read -p "Enter a year: " year
if [ -z "$year" ]; then
  echo "No year entered"
  exit 1
fi
if [[ "$year" =~ [a-zA-Z] ]]; then
  echo "Input must be numeric"
  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