Anyone know their stuff when it comes to Rewrite rules in Htaccess?

[O2C]

Hi All,

I have the following code in one of our Htaccess files and I'm not entirely sure what its doing. Could anyone shed some light and maybe explain the process its going through? I know its something to do with redirecting the urls dependant on the browser language.

RewriteCond %{REQUEST_URI} ^/(En|Es)$ [NC]

RewriteRule ^(En|Es)/(.*)$ $2?lang=$1 [L,R=301]

RewriteCond %{REQUEST_URI} !(.[a-zA-Z0-9]{1,5}|/)$

RewriteRule ^(.*)$ $1/ [L,R=301]

Thanks

[TrentonGreener]

Hey David,

Sorry for the delayed response on this.

Before we get started, I should point out that htaccess's syntax is very particular and you should be extremely careful when messing with it. even a single space out of place can cause massive errors. If you're planning changes, please consult with a developer or three on your team!

I think the best way to explain this is to go through exactly what the htaccess Rewrite calls are doing.

RewriteCond %{REQUEST_URI} ^/(En|Es)$ [NC]

RewriteCond - The condition of which a rewrite will take place
%{REQUEST_URI} - The URI that is requested from the server (everything after the domain and TLD i.e. moz.com/community 's URI would be /community)
^ - Denotes the beginning of a regular expression (regex)
/ - literally just /
(En|Es) - the '()' are simply a grouping and the '|' means OR. So this is saying En OR Es
$ - Denotes the end of a regex
[NC] - Means no case, so everything in this is not case sensitive

So literally this is saying execute this rewrite when the requested URI (after the .com or whatever TLD you use) is either /En OR /Es then whatever, with no attention to case

RewriteRule ^(En|Es)/(.*)$ $2?lang=$1 [L,R=301]

RewriteRule - The executed rule when the aforementioned RewriteCond is met.
^ - Denotes the beginning of a regular expression (regex)
(En|Es) - the '()' are simply a grouping and the '|' means OR. So this is saying En OR Es
/ - literally just /
(.) - This is a wildcard. Once again the () is a grouping, but here the . means zero or more arbitrary characters
$ - Denotes the end of a regex
$2 - this is the second captured grouping in this line. Meaning whatever is defined within (.*), which is everything after En/ or Es/
?lang= - this is literally writing '?lang=' without the 's.
$1 - this is the first captured grouping from this line. Meaning whichever En OR Es was captured will be written here.
[L] - Tells the server to stop rewriting after the preceding directive (rule) is processed
[R] - Instructs Apache to issue a redirect, causing the browser to request the rewritten URL
[301] - Corresponds to a Moved Permanetly Header Code
[L,R=301] - Combines all 3 of these into one.

For this I think it's easiest to just use an example.
moz.com/En/htaccess-is-fun will be our example
Since this url passes the RewriteCond, it goes on to the RewriteRule where it finds En OR Es and stores that value as $1 (En) then takes whatever is left and stores it as $2 (htaccess-is-fun).
It then writes htaccess-is-fun?lang=En and replaces the original selection (which is En/htaccess-is-fun) with the new rewrite making the result moz.com/htaccess-is-fun?lang=En . The new URL is served as a 301-ed redirect.

RewriteCond %{REQUEST_URI} !(.[a-zA-Z0-9]{1,5}|/)$

RewriteCond - The condition of which a rewrite will take place
%{REQUEST_URI} - The URI that is requested from the server (everything after the domain and TLD i.e. moz.com/community 's URI would be /community)
! - declares negation. i.e. "!cheese" matches everything except "cheese"
() - is again a grouping
\ - escapes a special character. So "." means a literal dot.
a-zA-Z0-9 - matches all lowercase letters, all uppcase letters, and all numbers
{1,5} - matches one to five of the previous designation. Meaning that there can be any combination of a-z, A-Z, or 0-9 in a sequence of one to five. i.e. A2ps OR 12345 OR AbC etc.
| - Means OR
/ - literally just /
$ - Denotes the end of a regex

RewriteRule ^(.*)$ $1/ [L,R=301]

^ - Denotes the beginning of a regular expression (regex)
(.) - This is a wildcard. Once again the () is a grouping, but here the . means zero or more arbitrary characters
$ - Denotes the end of a regex
$1 - this is the first captured grouping from this line.
/ - literally just /
[L] - Tells the server to stop rewriting after the preceding directive (rule) is processed
[R] - Instructs Apache to issue a redirect, causing the browser to request the rewritten URL
[301] - Corresponds to a Moved Permanetly Header Code
[L,R=301] - Combines all 3 of these into one.

So whenever the RewriteCond is met, this rule will select everything and then rewrite it as a 301 with a / trailing it.

Hope this helps! Let me know if you have any other questions.

Regards,
Trenton