Simple Log File Analyzer With Bash Scripting

Overview

Ever stared at a messy log file wondering where to begin? Whether you're a developer debugging an app or a sysadmin hunting down an issue, logs hold the truth, if only you could find it quickly.

That’s why I built Simple Log File Analyzer, a lightweight Bash script that helps you extract insights from your logs in seconds. With just one command, you’ll get a breakdown of INFO, WARNING, and ERROR messages, and even drill down into specific entries interactively. It’s a perfect project for anyone learning Bash or working with logs regularly.

What the Script Does

• Takes a log file path as input

• Validates the input and ensures the file exists and is readable

• Counts the number of occurrences of⁣ INFO, WARNING, and ERROR (case-insensitive)

• Displays a summary of the log level distribution

• Offers an interactive option for the user to view all messages of a specific log level

Script Code

#!/bin/bash

# Assign the first argument to a variable
LOG_FILE="$1"

# Argument and File Validation 
# Check for correct number of arguments
if [ "$#" -ne 1 ]; then
    echo "Error: Expected exactly one argument, but $# was given."
    echo -e "Usage:"
    echo -e "\tyes$0 <log_file_path>"   
    exit 1
fi

# Check if file exists and is readable
if [ ! -f "$LOG_FILE" ]; then
    echo "Error: File '$LOG_FILE' does not exist."
    exit 1
elif [ ! -r "$LOG_FILE" ]; then
    echo "Error: Access Denied. File '$LOG_FILE' is not readable."
    exit 1
fi

# Log Level Counting 
echo "Analyzing log file: $LOG_FILE..."

count_info=$(grep -owi "info" "$LOG_FILE" | wc -l)
count_error=$(grep -owi "error" "$LOG_FILE" | wc -l)
count_warning=$(grep -owi "warning" "$LOG_FILE" | wc -l)

# Summary Output 
echo -e "\nLog Analysis Summary for $LOG_FILE:"
echo "------------------------------------"
echo "INFO messages: $count_info"
echo "ERROR messages: $count_error"
echo "WARNING messages: $count_warning"

# Optional Message Viewing 
echo -e "\n" # Add a blank line for readability

read -p "Do you want to view messages of a specific type? (yes/no): " user_choice
user_choice=${user_choice,,} # Convert to lowercase

if [[ "$user_choice" == "yes" ]]; then
    read -p "Enter message type (INFO, WARNING, ERROR): " msg_type
    msg_type_lower=${msg_type,,} # Convert to lowercase for matching
    msg_type_display="${msg_type^^}" # Convert to uppercase for display (e.g., INFO)

    case "$msg_type_lower" in
        "info"|"warning"|"error")
            echo -e "\n------------------------------------"
            echo "${msg_type_display} messages:"
            grep -wi "$msg_type_lower" "$LOG_FILE"
            echo "------------------------------------"
            ;;
        *)
            echo -e "\nError: Invalid message type. Please enter INFO, WARNING, or ERROR."
            ;;
    esac
elif [[ "$user_choice" == "no" ]]; then
    echo -e "\nExiting. Goodbye!"
    exit 0
else
    echo -e "\nError: Invalid input. Please enter 'yes' or 'no'."
fi

Use Case

This tool is especially useful for:

• System administrators performing quick log audits

• Developers debugging application logs

• Security analysts checking for error trends or abnormal warning spikes

Key Features

• Robust argument and file validation

• Case-insensitive log level detection

• Simple, user-friendly interaction

• Easily extensible for more log levels or custom filters

Technologies Used

• Bash

• grep, wc, read, case, and other core Unix tools

How to Use the Script

1. Save the script to a file, for example, log_analyzer.sh

2. Make the script executable:

sudo chmod +x log_analyzer.sh

3. Run the script with a log file path as an argument:

./log_analyzer.sh /path/to/your/logfile.log

4. Follow the prompts.

   The script will display a summary of the log levels. You will be asked if you want to view messages of a specific type; just type yes or no.
   If yes, enter one of: INFO, WARNING, or ERROR to view those messages.

Example Output

Conclusion:

Bash scripting doesn’t have to be complicated to be powerful. This project shows how a few lines of code can make your workflow faster, cleaner, and more insightful, especially when dealing with log files.

I hope this inspires you to explore automation and log parsing further. You can easily extend this script to support timestamps, export results, or analyze multiple log files at once. If you found this helpful or have ideas for improvement, feel free to connect or drop a comment below!