Monitor Log File for Keywords and Count Occurrences

#!/bin/bash

LOG_FILE="/var/log/nginx/access.log"
KEYWORDS=("error" "warning" "failed")
COUNT=0

echo "Monitoring log file: $LOG_FILE for keywords: ${KEYWORDS[*]}"

tail -F "$LOG_FILE" | while read LINE; do
  for KEYWORD in "${KEYWORDS[@]}"; do
    if [[ "$LINE" =~ "$KEYWORD" ]]; then
      echo "[$(date +'%Y-%m-%d %H:%M:%S')] Found '$KEYWORD': $LINE"
      ((COUNT++))
      echo "Total matches found: $COUNT"
      break # Exit inner loop once keyword is found in line
    fi
  done
done

How it works: This script uses `tail -F` to follow a log file in real-time, displaying new lines as they are appended. It then pipes each new line to a `while read LINE` loop. Inside the loop, it iterates through a list of defined `KEYWORDS`. If a line contains any of the keywords, it prints the line with a timestamp and increments a counter. This is highly useful for real-time debugging, tracking specific events, or monitoring server health by looking for critical messages.