🚀 Log Analyzer and Report Generator Challenge

🖥️ The Scenario

You're a system administrator managing a network of servers. Each day, these servers generate log files full of system events and error messages.

Your task? Build a Bash script to analyze these logs and produce a daily summary report. This script will save time, automate log analysis, and ensure you never miss critical events!

🎯 Script Objectives

Your Bash script will do the following:

✅ Take a log file as input (via command-line arguments).
🔎 Count error messages with keywords like ERROR or Failed.
🚨 Highlight critical events containing the keyword CRITICAL (with line numbers).
📊 Identify the top 5 error messages and their counts.
📝 Generate a summary report with all findings in a text file.
📦 Optional: Archive or move processed logs to a designated directory for cleanup.

🛠️ Bash Commands Explained

Here’s how the script works step by step, with commands to get you started!

1️⃣ Reading the Log File

Command: cat
- Usage: cat /path/to/logfile.log
- What it does: Displays the entire content of the log file. Useful for verifying the file’s content before processing.
- Example:
```
  cat logfile.log
```
Command for checking existence: if
- Usage:
```
  if [ -f logfile.log ]; then
      echo "File exists!"
  else
      echo "File not found!"
  fi
```
- What it does: Checks if the file exists before processing. Prevents errors if the file is missing.

2️⃣ Counting Errors

Command: grep
- Usage: grep -i "ERROR" logfile.log | wc -l
- What it does:
  - grep -i "ERROR": Searches for all lines containing "ERROR" (case-insensitive with -i).
  - wc -l: Counts the number of lines returned by grep.
- Example:
```
  error_count=$(grep -i "ERROR" logfile.log | wc -l)
  echo "Total errors: $error_count"
```

3️⃣ Finding Critical Events

Command: grep -n
- Usage: grep -n "CRITICAL" logfile.log
- What it does:
  - -n: Displays the line number along with the matching lines.
- Example:
```
  grep -n "CRITICAL" logfile.log
```
  Output:
```
  45:CRITICAL: Disk space low
  87:CRITICAL: Service timeout
```

4️⃣ Top 5 Error Messages

Command: awk + sort + uniq
- Usage:
```
  grep -i "ERROR" logfile.log | awk '{print $0}' | sort | uniq -c | sort -nr | head -5
```
- Explanation:
  1. grep -i "ERROR": Finds all error lines.
  2. awk '{print $0}': Prints the entire line.
  3. sort: Sorts the lines alphabetically.
  4. uniq -c: Groups identical lines and counts their occurrences.
  5. sort -nr: Sorts the output numerically in descending order.
  6. head -5: Displays the top 5 most common error messages.
- Example Output:
```
  20 ERROR: Service unavailable
  15 ERROR: Connection timeout
  10 ERROR: Disk space low
```

5️⃣ Generating a Summary Report

Command: echo + Redirection (> or >>)

Usage:

  echo "Date of Analysis: $(date)" > summary_report.txt
  echo "Log File: logfile.log" >> summary_report.txt
  echo "Total Errors: $error_count" >> summary_report.txt
  echo "Critical Events:" >> summary_report.txt
  grep -n "CRITICAL" logfile.log >> summary_report.txt

What it does: Creates a report with all the key details in a text file.
- >: Creates/overwrites the file.
- >>: Appends to the file.

6️⃣ Archiving Processed Logs (Optional)

Command: mv or gzip
- Move the processed log file to an archive folder:
```
  mv logfile.log /path/to/archive/
```
- Compress the log file:
```
  gzip logfile.log
```

📝 Sample Summary Report

Here’s what your final report might look like:

Date of Analysis: Tue Feb 13 2025
Log File: logfile.log
Total Lines Processed: 12345
Total Errors: 205
Top 5 Error Messages:
   20 ERROR: Service unavailable
   15 ERROR: Connection timeout
   10 ERROR: Disk space low
Critical Events:
   45:CRITICAL: Disk space low
   87:CRITICAL: Service timeout