htaccess redirect from www to non-www - regex

Question

I am new to this.
Code from my .htaccess file goes like this:
RewriteEngine on
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule .* index.php/$0 [PT,L]
RewriteCond %{HTTP_HOST} ^www\.(.+) [NC]
RewriteRule ^(.*) http://%1/$1 [R=301,NE,L]
Redirect 301 /abc/ /abcnew/
I want this to redirect from www to non-www i.e., from http://www.example.com to http://example.com
I copied:
RewriteCond %{HTTP_HOST} ^www\.(.+) [NC]
RewriteRule ^(.*) http://%1/$1 [R=301,NE,L]
this code from here Generic htaccess redirect www to non-www.
I also checked in /etc/apache2/mods-enabled folder on my linux server. There "rewrite.load" this module is present.(I think this might mean that rewrite is enabled on my server, but correct me if I am wrong.)
Redirect 301 /abc/ /abcnew/
and just FYI this above code works fine(its redirecting my old links to new links).
I also tried this.
RewriteCond %{HTTP_HOST} ^www\.example\.com [NC]
RewriteRule ^(.*)$ http://example.com/$1 [L,R=301]
Doesn't work for me.
Please help. Thanks in advance...
Edit:
this link I found this. But not sure what should be edited. Can anyone please point out.?

Answer 1

You need to place external (full) redirect rules before internal rewrite ones and also make sure to use mod_rewrite rules only.
Try this:
RewriteEngine on
RewriteBase /
RewriteCond %{HTTP_HOST} ^www\.(.+) [NC]
RewriteRule ^(.*) http://%1/$1 [R=301,NE,L]
RewriteRule ^abc/?$ /abcnew/ [L,NC,R=301]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule .* index.php/$0 [PT,L]

Answer 2

RewriteCond %{HTTPS} off
RewriteCond %{HTTP_HOST} ^www\.(.*)$ [NC]
RewriteRule ^(.*)$ http://%1/$1 [R=301,L]
RewriteCond %{HTTPS} on
RewriteCond %{HTTP_HOST} ^www\.(.*)$ [NC]
RewriteRule ^(.*)$ https://%1/$1 [R=301,L]