Extract and Count Specific Patterns in Log Files

#!/bin/bash

LOG_FILE="$1"
SEARCH_PATTERN="$2"

# Check for required arguments
if [ -z "$LOG_FILE" ] || [ -z "$SEARCH_PATTERN" ]; then
    echo "Usage: $0 <log_file> <search_pattern>"
    echo "Example: $0 /var/log/nginx/access.log \"GET /api/v1/user\""
    exit 1
fi

# Validate if the log file exists
if [ ! -f "$LOG_FILE" ]; then
    echo "Error: Log file '$LOG_FILE' not found." >&2
    exit 1
fi

echo "Searching for '$SEARCH_PATTERN' in '$LOG_FILE'...
"
# Count total occurrences of the pattern
COUNT=$(grep -c "$SEARCH_PATTERN" "$LOG_FILE")
echo "Total occurrences of pattern: $COUNT"

# Show unique lines containing the pattern
echo "
Unique lines containing the pattern (first 10):"
grep "$SEARCH_PATTERN" "$LOG_FILE" | sort -u | head -n 10

# Example: If the pattern is an IP address, count occurrences of each unique IP
# Basic regex for IPv4 address
if [[ "$SEARCH_PATTERN" =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
    echo "
Counting occurrences of each unique matching IP address (top 10):"
    grep -oE "$SEARCH_PATTERN" "$LOG_FILE" | sort | uniq -c | sort -nr | head -n 10
elif [[ "$SEARCH_PATTERN" =~ ^[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}$ ]]; then
    echo "
Counting occurrences of each unique matching email address (top 10):"
    grep -oE "$SEARCH_PATTERN" "$LOG_FILE" | sort | uniq -c | sort -nr | head -n 10
fi