Bash script to check presence of specific response header

check-response-header.sh

#!/bin/bash

# Use case: measure CDN change propagation time (CPT)
# Change the CDN config in CDN control panel or API, 
# so CDN servers a new response header.
# Next, run this script to check after how many seconds
# the CDN serves a response with that header
# For example, change CDN config to start serving the x-cdn header
# Run this script then with command
# ./check_header.sh HEADER=x-cdn DEBUG=1

# Default values for the variables
DEFAULT_URL='https://cdnpnodes.mncdn.com/static/15kb.png'
DEFAULT_HEADER='date'
DEFAULT_DEBUG=1
DEFAULT_MAX_TIME=90

# Assign command-line arguments or use defaults
for arg in "$@"; do
  case $arg in
    URL=*) URL="${arg#*=}" ;;
    HEADER=*) HEADER="${arg#*=}" ;;
    DEBUG=*) DEBUG="${arg#*=}" ;;
    MAX_TIME=*) MAX_TIME="${arg#*=}" ;;
    *) echo "Invalid argument: $arg" ;;
  esac
done

# Set defaults if not provided
URL=${URL:-$DEFAULT_URL}
HEADER=${HEADER:-$DEFAULT_HEADER}
DEBUG=${DEBUG:-$DEFAULT_DEBUG}
MAX_TIME=${MAX_TIME:-$DEFAULT_MAX_TIME}

COUNT=0  # Initialize request counter
START_TIME=$(date +%s)  # Record the start time

# Echo the test settings
echo -e "Test settings:\nURL: $URL\nHEADER: $HEADER\nDEBUG: $DEBUG\nMAX_TIME: $MAX_TIME seconds\n"

while true; do
  CURRENT_TIME=$(date +%s)
  ELAPSED_TIME=$((CURRENT_TIME - START_TIME))
  
  # Check if the elapsed time has exceeded the max time
  if [ "$ELAPSED_TIME" -ge "$MAX_TIME" ]; then
    echo -e "\nHeader $HEADER not found within $MAX_TIME seconds."
    break
  fi
  
  COUNT=$((COUNT + 1))
  
  # Send the HTTP request and capture the headers separately
  response_headers=$(mktemp)
  curl -s -D "$response_headers" -o /dev/null "$URL"
  
  # Extract the status code for both HTTP/1.1 and HTTP/2
  status_code=$(awk '/HTTP\// {print $2}' "$response_headers" | head -n1)
  
  # Check if the specific header is present with exact matching (case-insensitive)
  if grep -iq "^$HEADER: " "$response_headers"; then
    echo -e "$status_code, Header $HEADER found!\n"
    # Print all response headers
    cat "$response_headers"
    echo -e "\nNumber of requests made: $COUNT"
    echo -e "Script run time (seconds): $ELAPSED_TIME\n"
    rm "$response_headers"  # Clean up temporary file
    break
  else
    echo -e "$status_code, Header $HEADER not found\n"
    # Print all response headers if DEBUG is enabled
    if [ "$DEBUG" -eq 1 ]; then
      cat "$response_headers"
    fi
    rm "$response_headers"  # Clean up temporary file
  fi
  
  # Wait for 5 seconds before the next request
  sleep 5
done