Can I check for maintenance mode before redirecting to subdomain?

Each time that WordPress inserts a blog into maintenance mode, it creates a file in the root of your installation directory.

the file contains a string related to the plugin/theme/core that is being updated. Its name is .maintenance (doesn’t have a name, only extension).

The file stays there until the process is over, therefore you can check if the file exists by doing this:

if( file_exists(ABSPATH .'/.maintenance') ) { 
    // Stop redirection here
}

Which would be what you are looking for.

Related Posts:

  1. Host the wp-admin on another domain?
  2. Site redirects to wrong url when saving settings
  3. Force WordPress to load from site’s hostname
  4. Some admin pages redirecting to front page on save
  5. Two WordPress installations: One in root and one in sub directory – no images in subdir installation [closed]
  6. How to redirect the frontend of a WordPress site (only)?
  7. Permalinks do not include www subdomain
  8. When i try to enter subdomain i’m redirected to main domain
  9. Can’t login to WordPress admin panel after changing domain to use WordPress pages as a fallback from React
  10. Need to redirect from Apache2 Ubuntu Default Page to home page in wordpress
  11. I have cloudflare flexible enabled, How to redirect to https for Nginx server
  12. How to Block WordPress from subdomain?
  13. Top-level staging-site URL redirects to a different site
  14. Redirect Restricted Page to 404
  15. Redirect user to original url after login?
  16. Redirect to dashboard after login
  17. Make a video post redirect to next post after completion
  18. Redirect blog page to latest post?
  19. WordPress site redirects to different wordpress domain on the same server after reuploading db backup
  20. WordPress Redirect based on the prescence of a cookie
  21. Links to an exisiting Page are now redirecting to a draft page?
  22. Random and Erroneous WordPress Redirect
  23. Redirect Old domain & posts to new domain homepage
  24. Redirecting users to referrer page after logging in using custom login form
  25. Remove lost password form and URL
  26. add_rewrite_rule to pass entire path as a single parameter
  27. What is the wordpress way of displaying local external content?
  28. Menu links only using http after enabling https, unable to redirect http links
  29. Redirects from Tumblr to new WP
  30. Why does multisite bypass WordPress for wp-content, wp-admin, wp-includes and .php files?
  31. Redirecting to old domain, tried everything, nothing works
  32. How to modify the Register link in the login page?
  33. WordPress redirecting to 127.0.0.1 when accessing the site from a remote device
  34. Redirect a page id url but not the page slug
  35. Redirect based on parameter in url
  36. Stop wordpress redirecting www to non-www
  37. WordPress Global Redirect
  38. Why does wp_redirect strip out %0A (url encoded new line character) and how do I make it stop?
  39. Redirect Logged In User if page is wp-login.php and $_Get[‘level’] = X
  40. WordPress url incomplete redirects to first article with that name
  41. Redirect loop after changing nameserver [closed]
  42. Is it possible to incorporate username in a login redirect?
  43. How to make wordpress folder (/wordpress) redirect to /?
  44. Changing domain
  45. Redirecting amp url to non amp url
  46. Redirect htaccess does not work correctly with my new wordpress site
  47. Remove #wpcf7-f2450-o1 with Contact form 7 redirect [closed]
  48. Some posts from custom post type to subdomains
  49. How do I put up a splash page and have all WordPress links redirect to this page?
  50. W3 Cache redirects to front page when I press purge all caches
  51. Stop forcing certain paths to end with a forward slash
  52. Redirection on Custom page
  53. How do I redirect users after submitting a topic for moderation?
  54. Direct iPhone visitors to different stylesheet?
  55. How to delete a post and keep its slug to refer to another post
  56. 301 redirect any RSS feed on level up url
  57. Redirect loop with similar URLs
  58. Why does WP HTTP API switch the method (POST/PURGE) to GET when redirecting (302)?
  59. Redirect user to specific link after login
  60. 301 redirect via htaccess rules on the new site
  61. WordPress Domain redirects to different host
  62. Change the domain url?
  63. After retrive password, redirect to index page
  64. Change Category Slug Redirection
  65. custom login form redirect problem
  66. WordPress redirect to new domain name
  67. Bulk redirect all post
  68. Disable redirect to homepage after successful Login, Stay on Current Page
  69. WordPress no permission redirection to a popup
  70. Open wordpress page in directory the way index.html would open
  71. How force WordPress redirect to current custom page after login
  72. Redirect Homepage to another page when user login
  73. Site using static homepage, redirects (301) and removes pluses from query string
  74. Unusual Apache2 Error Causing WordPress Redirect Error?
  75. Determine user destination on wp-login.php
  76. 301 Redirect Loop www to non-www – Nginx + Apache2
  77. 301 Redirect in WordPress not working in htaccess
  78. Toggle Redirect Function On/Off With Checkbox
  79. My wordpress site has “https://” on it but when I go to Dashboard and click visit site, it removes the “https://”
  80. After disabling Multisite, homepage redirects to non-existing page
  81. redirect to https://my-site/wp-admin/ instead of https://my-site/wordpress/wp-admin/ after options updating
  82. Redirect after login when WordPress in subdirectory
  83. All links redirecting to homepage
  84. How to redirect non-admin/editors from specific pages?
  85. How to make a redirect link in wordpress?
  86. wp_redirect leading to an infinite loop
  87. Redirect after Permalink change – What regex do I use?
  88. Configure WordPress to listen on a port other than 80
  89. Redirect based on $_GET parameters
  90. Logging back into WordPress after logging out and having issues with ‘loggedout=true’ in redirect URL
  91. redirect users to the login page
  92. Redirect posts to sub domain except pages
  93. Moving an ASP Site to WordPress – Looking for Help on Redirects
  94. WordPress subfolders htaccess bypassing the root htaccess RewriteRule
  95. WordPress Redirecting Form Action to Home Page
  96. Redirect to Homepage if URL contains string
  97. How to setup an automatic redirect for when there has been a critical error on the site?
  98. How to force HTTP and stop SSL completey on WordPress website
  99. How to Setup 2 Domains on a Single WordPress (Regions Filter)?
  100. WordPress keeps redirecting to root site after saving any setting