Automate Nginx Configuration Reload on Changes

#!/bin/bash

# --- Configuration Start ---
NGINX_CONF_DIR="/etc/nginx"
# Main Nginx config file or directory to monitor for changes
# For single file: NGINX_CONFIG_TARGET="$NGINX_CONF_DIR/nginx.conf"
# For a directory with multiple configs (e.g., sites-enabled): NGINX_CONFIG_TARGET="$NGINX_CONF_DIR/sites-enabled"
NGINX_CONFIG_TARGET="$NGINX_CONF_DIR"

# Path to the Nginx executable (usually /usr/sbin/nginx or /usr/local/nginx/sbin/nginx)
NGINX_BIN="/usr/sbin/nginx"

# Interval (in seconds) to check for changes if not using inotifywait
CHECK_INTERVAL=5
# --- Configuration End ---

LAST_MD5=""

# Function to calculate MD5 sum of target files/directory
calculate_md5() {
  if [ -d "$NGINX_CONFIG_TARGET" ]; then
    find "$NGINX_CONFIG_TARGET" -type f \( -name "*.conf" -o -name "*.inc" \) -print0 | sort -z | xargs -0 cat | md5sum | awk '{print $1}'
  elif [ -f "$NGINX_CONFIG_TARGET" ]; then
    md5sum "$NGINX_CONFIG_TARGET" | awk '{print $1}'
  else
    echo "Error: NGINX_CONFIG_TARGET '$NGINX_CONFIG_TARGET' is neither a file nor a directory." >&2
    exit 1
  fi
}

echo "Monitoring Nginx configuration files in '$NGINX_CONFIG_TARGET' for changes..."

while true; do
  CURRENT_MD5=$(calculate_md5)

  if [ -z "$LAST_MD5" ]; then
    LAST_MD5="$CURRENT_MD5"
    echo "Initial MD5 hash established."
  fi

  if [ "$CURRENT_MD5" != "$LAST_MD5" ]; then
    echo "
--- Nginx configuration change detected! ---"
    echo "Current MD5: $CURRENT_MD5"
    echo "Previous MD5: $LAST_MD5"

    echo "Testing Nginx configuration syntax..."
    "$NGINX_BIN" -t
    if [ $? -eq 0 ]; then
      echo "Nginx configuration syntax is OK. Reloading Nginx..."
      "$NGINX_BIN" -s reload
      if [ $? -eq 0 ]; then
        echo "Nginx reloaded successfully!"
        LAST_MD5="$CURRENT_MD5"
      else
        echo "Error: Failed to reload Nginx. Configuration not applied." >&2
      fi
    else
      echo "Error: Nginx configuration syntax failed. Changes not applied." >&2
      # Revert LAST_MD5 to prevent continuous re-attempts on bad config
      # LAST_MD5="$CURRENT_MD5" # Uncomment to keep trying until fixed
    fi
  else
    echo -n "."
  fi

  sleep "$CHECK_INTERVAL"
done