Use $wp_filter global to view functions attached to actions and filters

how-not-to-use-wp-filter.php

<?php
/*
Plugin Name: wp_filter functions
Plugin URI: http://www.damiencarbery.com/2017/06/list-functions-attached-to-an-action/
Description: List functions attached to all actions and filters. DON'T DO IT!
Author: Damien Carbery
Version: 0.1
*/

add_action( 'wp_head', 'wp_filter_the_wrong_way' );
function wp_filter_the_wrong_way() {
  global $wp_filter;
  
  // Do NOT do this - it will render many MB of content.
  echo '<!-- ', var_export( $wp_filter, true ), ' -->';
}

wp-filter-for-one-action.php

<?php
/*
Plugin Name: genesis_entry_content functions
Plugin URI: http://www.damiencarbery.com/2017/06/list-functions-attached-to-an-action/
Description: List functions attached to genesis_entry_content.
Author: Damien Carbery
Version: 0.1
*/

add_action( 'wp_head', 'wp_filter_for_one_action' );
function wp_filter_for_one_action() {
  global $wp_filter;

  echo '<!-- ', var_export( $wp_filter[ 'genesis_entry_content' ], true ), ' -->';
}

wp-filter-genesis_entry_content-output.html

<!-- WP_Hook::__set_state(array(
   'callbacks' => 
  array (
    8 => 
    array (
      'genesis_do_post_image' => 
      array (
        'function' => 'genesis_do_post_image',
        'accepted_args' => 1,
      ),
    ),
    10 => 
    array (
      'genesis_do_post_content' => 
      array (
        'function' => 'genesis_do_post_content',
        'accepted_args' => 1,
      ),
    ),
    12 => 
    array (
      'genesis_do_post_content_nav' => 
      array (
        'function' => 'genesis_do_post_content_nav',
        'accepted_args' => 1,
      ),
    ),
    14 => 
    array (
      'genesis_do_post_permalink' => 
      array (
        'function' => 'genesis_do_post_permalink',
        'accepted_args' => 1,
      ),
    ),
    20 => 
    array (
      'bch_add_store_custom_field_info' => 
      array (
        'function' => 'bch_add_store_custom_field_info',
        'accepted_args' => 1,
      ),
    ),
  ),
   'iterations' => 
  array (
  ),
   'current_priority' => 
  array (
  ),
   'nesting_level' => 0,
   'doing_action' => false,
)) -->