Answers for "how to redirect to login page if user not logged on in wordpress"

if user logged in wordpress

if ( is_user_logged_in() ) {
   // your code for logged in user 
} else {
   // your code for logged out user 
}

how to redirect from home page to custom link if not logged in in wordpress

add_action( 'admin_init', 'redirect_if_user_not_logged_in' );

function redirect_if_user_not_logged_in() {

if ( !is_user_logged_in() && is_page('slug') ) {

      wp_redirect( 'http://your-redirect-page-here '); 
   
   exit;
   }
}

how to check if user is logged in wordpress

<?php 
if ( is_user_logged_in() ) {
  echo 'Welcome, logged in user. <a href="'.wp_logout_url().'">Click here to logout</a>.';
}else{
  echo 'Please login by <a href="'.wp_login_url().'">clicking here</a>.'
}