Download MP4s follow redirects

download_mp4s.sh

#!/bin/bash
#
# Downloads MP4 files from a specified webpage URL provided as a command-line argument,
# following redirects. It requires 'curl' for operation. If 'curl' is not found, it
# advises the user to install it.
#
# Usage:
#   ./download_mp4s.sh <URL>

check_for_curl() {
  if ! command -v curl &> /dev/null; then
    echo "'curl' is required but not installed. Please install 'curl' and try again."
    exit 1
  fi
}

download_file() {
  local url="$1"
  echo "Downloading ${url} with curl..."
  curl -LO "${url}"
}

fetch_html_content() {
  local url="$1"
  curl -Ls "${url}"
}

parse_mp4_links() {
  local html="$1"
  # This pattern looks for href attributes that end with .mp4, accounting for potential HTML entity encoding within the href value.
  # Use egrep in case we're on macOS
  echo "${html}" | egrep -o 'href="[^\"]+\.mp4"' | cut -d'"' -f2
}

main() {
  if [ "$#" -ne 1 ]; then
    echo "Usage: $0 <URL>"
    exit 1
  fi

  local url="$1"

  check_for_curl

  local html=$(fetch_html_content "${url}")
  local links=$(parse_mp4_links "${html}")

  for link in ${links}; do
    if [[ "${link}" =~ ^http ]]; then
      download_file "${link}"
    else
      # Assuming the provided URL is the base path for relative links
      local absolute_link=$(printf "%s%s" "${url}" "${link}")
      download_file "${absolute_link}"
    fi
  done

  echo "Download completed."
}

main "$@"