Add/remove CRON action depending on variable

I am not sure why the remove_action isn’t working because by the looks of your code, it should. Alternatively, you can add the conditional logic to your generate_sitemap() 

function generate_sitemap() {

    global $create_sitemap;

    if ( $create_sitemap ) return false;

    $sitemap = '<?xml version="1.0" encoding="UTF-8"?>';
    $sitemap .= '<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">';

    // Get a query of all jobs that are available
    $all_jobs = new WP_Query( array( 'post_type' => 'job_listing', 'post_status' => 'publish', 'posts_per_page' => -1 ) );

    // Add the URL and last modified time (in GMT) to the sitemap
    foreach( $all_jobs->posts as $post ){
        $sitemap .= '<url>';
        $sitemap .= '<loc>' . get_the_permalink( $post->ID ) . '</loc>';
        $sitemap .= '<lastmod>' . date( 'c', strtotime( $post->post_modified_gmt ) ) . '</lastmod>';
        $sitemap .= '</url>';
    }

    $sitemap .= '</urlset>';

    // Write the sitemap to yoursite.com/job-sitemap.xml
    $fp = fopen(ABSPATH . 'job-sitemap.xml', 'w');
    fwrite($fp, $sitemap);
    fclose($fp);
}

Make sure $create_sitemap is accessible within the function.

Related Posts:

  1. add_action(), add_filter() before or after function
  2. Trouble understanding apply_filters()
  3. What is the very earliest action hook you can call?
  4. wp_headers vs send_headers. When to use each?
  5. How many filter/action hooks are healthy?
  6. Earliest hook to reliably get $post/$posts
  7. What does (10, 2) mean when used with add_filter
  8. Valid characters for actions, hooks and filters
  9. How to check if a hook is hooked or not?
  10. Is it possible to use object in add_action?
  11. Hook into admin post list page
  12. Anyway to edit the titlebar of WordPress Widgets in the Admin area?
  13. How do I know if author field was changed on post save?
  14. Using hooks to place content in theme dynamically
  15. About Hooks and Filters
  16. PHP5, Inheritance, Singleton – action & filter hook limitations
  17. Should I use add_action(‘publish_post or add_filter(‘publish_post?
  18. Please explain me what the do_action does
  19. Apply the_title filter to post titles AND backend auto social-sharing plugin, but not nav menu
  20. add_action uses ‘echo’ add_filter uses ‘return’, why?
  21. Cron schedule interval through plugin options?
  22. Too many actions/filters!
  23. How to get list of all hooks of current theme / plugin?
  24. Making a class available via actions filters
  25. How does WordPress call functions attached to a certain action hook before calling functions attached to other hooks
  26. How to get current action?
  27. Conditionally call add_action depending on post_type?
  28. how to change appearence of the content of default post list columns?
  29. Filter list by a unique meta value dilemma
  30. return values from hooks do_action and apply_filters, which is better
  31. How to get all the predefined do_action() calls from an active theme
  32. Is it possible to track down Actions and Filters?
  33. Return a custom value in a function added to an action hook
  34. How to call a function or method that is Namespaced using another plugin
  35. How to change currency programmatically on creating order action?
  36. add filter login_redirect does not contain original requested redirect
  37. get_header and hook avoid normal call
  38. Can the wp_filter object hold multiple values with the same key
  39. How to change the order (priority) of registered filters (or actions) (e.g. for the_content)?
  40. apply_filters/do_action tag characters limit
  41. Replace a word with a word in the URL string
  42. Is there a filter called ‘network_admin_init’?
  43. How to add ‘total’ value to custom column title on the posts list page
  44. Filter taxonomy admin pagination
  45. When to use add_action when registering/enqueuing scripts
  46. Are there actions or filters I can use for Ajax calls?
  47. Correct method of redirecting user login
  48. Shortcodes — Using add_action, add_filter in the shortcode
  49. How to remove action with slashes and arrows?
  50. How do I use remove_action on an add_action that uses an array?
  51. How to properly modify WP Vary or any existing headers?
  52. Changing WordPress core without hacking core
  53. Building a request processor for multi-page forms, etc using $_GET requests
  54. Comment search plugin
  55. Proper after_setup_theme and wp_head cleanup
  56. How can I output all apply_filters and do_action?
  57. Add a filter inside an action init
  58. Is it possible to apply_filter on a wp_ajax_ action?
  59. Filter for when the post is updated
  60. How can I specify the post status of an untrashed post?
  61. Filter get_page_by_path()
  62. Remove actions/filters that are set with create_function()
  63. Get The Caller (Plugin / Theme / Core) For All actions & Hook in WordPress
  64. Alter existing page contents based on url
  65. How to access page variable inside action hook
  66. Register new user, assign custom role then send email
  67. How to include add_filter() in a condition based on $post data
  68. Admin: how to make a custom list filter button send GET queryvars
  69. What is the action hook to use if you want to capture the new password during password change?
  70. Use has_filter on comment_post
  71. Echo string in admin panel footer beside version no
  72. How to change default text for specific post type
  73. What is the action or filter for adding information under the Permalink in Edit Post/Page?
  74. alternative to the_content filter
  75. output custom Posts on a Page
  76. How to pass a variable between filter/action functions?
  77. style_loader_tag not changing stylesheet to preload
  78. Adding link options in insert/edit link dialog window
  79. How to redirect a unique link based on login status
  80. Hook to change the site URL
  81. Hook to add content after date in post?
  82. add_action with associative array
  83. how to use apply filter for Class?
  84. How can I see exactly what arguments are being passed through a filter so that I may modify them?
  85. WordPress set featured image to first image of the post
  86. adding an action inside if condition not working
  87. Using add_filters() , apply_filter(), add_action() and do_action() in extending a plugin
  88. What action/filter can be used for modifying the page to be rendered?
  89. What problems could happen if I replaced add_filter and add_action with the function calling
  90. check, if any “add_action” function contains string XXXXXXXXX
  91. Custom search fields and AJAX support
  92. Adding to an array & passing it through do_action/apply_filters
  93. Hook into ‘when user logs in’ [persistent login]
  94. Custom registration field to SQL database
  95. Updating User Profile on Registration
  96. How would I remove an inline googleAPI font script in the the parent theme header.php?
  97. can’t output gray scaled image I’ve created using add_image_size
  98. Is it possible to make get variable out of filter in Class?
  99. GET form action. Redirect to self
  100. Can you call a filter hook by “add_action”?