Mod Rewrite

mod_rewrite

Uses • • • • •

Obscure original URLs Clean URLs SEO (Seriously.) Redirection Access control

Where can I place rewrite rules? • • • •

httpd.conf (or included config files) VirtualHost Directory* .htaccess

*Certain restrictions apply.** **Use .htaccess files

Directives • • • • • • •

RewriteEngine RewriteOptions RewriteRule RewriteCond RewriteLog RewriteBase ...and more! (that we won’t cover)

Exhibit A #

Default WordPress rewrite rules

RewriteEngine On RewriteBase / RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule . /index.php [L]

Exhibit A, Explained #

Default WordPress rewrite rules

# Turn rewrite engine on RewriteEngine On # Base all rewrites on ‘/’ URL RewriteBase / # If the requested file does not exist RewriteCond %{REQUEST_FILENAME} !-f # ...or if no directory exists... RewriteCond %{REQUEST_FILENAME} !-d # Rewrite the URL to /index.php RewriteRule . /index.php [L]

RewriteEngine on | off • •

Enables or disables the runtime rewriting engine Required inside VirtualHost and .htaccess

RewriteRule pattern substitution [flags]

• • • •

Can occur more than once Processed in order First rule processed on URL path Subsequent rules processed on previous output

•

Think of chaining commands together in bash

RewriteRule pattern substitution [flags]

• • •

PCRE (Perl-Compatible Regular Expressions) Matches the URL path RewriteCond required to match anything else

Regex

[\t])*(?:[^()<>@,;:\\" .\[\] \000-\031]+(?:(?:(?:\r\n)?[\t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\ [\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*(?:,@(?:(?:\r\n)?[\t])*(?:[^()<>@,;:\\".\ [\] \000-\031]+(?: (?:(?:\r\n)?[\t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?: (?:\r\n)?[\t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[\t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))| \[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[\t])*)?(?:[^()<>@,;:\\".\[\] \0 00\031]+(?:(?:(?:\r\n)?[\t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\ .|(?:(?:\r\n)?[\t]))*"(?: (?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[\t])+|\Z| (?=[\["()<>@,;:\\".\[\]]))|"(? :[^\"\r\\]|\\.|(?:(?:\r\n)?[\t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r \n)?[ \t])* (?:[^()<>@,;:\\".\[\]\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\ [([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[\t])*(?:[ ^()<>@,;:\\".\[\] \000-\031]+ (?:(?:(?:\r\n)?[\t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*\> (?:(?:\r\n)?[\t])*)(?:,\s*( ?:(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[\t])+|\Z|(?=[\["() <>@,;:\\ ".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[\t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:( ?:\r\n)?[\t]) *(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\ \]|\\.|(?:(?:\r\n)?[\t]))*"(?:(?:\r\n)?[ \t ])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\]\000\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[\t])*) (? :\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\]\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\ \".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[\t])*))*|(?: [^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r \n)?[\t])+|\Z|(?=[\["()<>@,;:\\".\[\ ]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[\t]))*"(?:(?:\r\n)?[ \t])*) *\<(?:(?:\r\n) ?[\t])*(?:@(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[\t])+|\Z|(?=[\["()<>@,;:\ \".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[\t])*)(?:\.(?:(?:\r\n) ?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)? [\t])*))*(?:,@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\]\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["() <>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[\t])*)(?:\.(?:(?:\r\n)?[ \t] )*(?:[^()<>@,;:\ \".\[\]\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?: \r\n)?[ \t])*))*)*:(?:(?:\r\n)?[\t])*)? (?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[\t])+|\Z|(? =[\["()<>@,;:\\". \[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[\t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?: \r \n)?[\t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?: [^\"\r\\]|\\.|(?:(?:\r\n)?[\t]))*"(?:(?:\r\n)?[ \t]) *))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)? [\t])*)(?:\ .(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\]\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["() <>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[\t])*))*\>(?:( ?:\r\n)?[ \t])*))*)?;\s*)

Regex

(RFC 822 Compliant Email Validation)

Regex

®

It’s Not That Hard™

RewriteRule pattern substitution [flags] Can be one of several things:

• • • •

file-system path URL path Absolute URL - [dash]

(no substitution)

RewriteRule pattern substitution [flags]

• • •

Affect behavior of the Rule or Condition Contained in square brackets Comma-separated

[NC] [NC, QSA, L]

RewriteRule pattern substitution [flags] C

Chain this rule to the next rule

E

Set environment variable

F

403 Forbidden Status

G

410 Gone Status

H

Specify handler

L

Don’t process rules after this one

NC QSA R[=301]

Case-insensitive Append query string Redirect (R=HTTP Status Code)

RewriteCond variable pattern [flags]

• • •

HTTP Server Variables (HTTP_HOST, REQUEST_URI) Pattern that must match the given variable Optional flags that change the behavior, just like RewriteRule

RewriteCond variable pattern [flags] HTTP_REFERER HTTP_HOST REMOTE_ADDR REQUEST_METHOD SERVER_PORT HTTP_USER_AGENT REQUEST_URI etc.

Exhibit A, Explained (Again) #

Default WordPress rewrite rules

# Turn rewrite engine on RewriteEngine On # Base all rewrites on ‘/’ URL RewriteBase / # If the requested file does not exist RewriteCond %{REQUEST_FILENAME} !-f # ...or if no directory exists... RewriteCond %{REQUEST_FILENAME} !-d # Rewrite the URL to /index.php RewriteRule . /index.php [L]

non-www to www RewriteEngine On RewriteCond %{HTTP_HOST} ^example\.com$ [NC] RewriteRule ^(.*)$ http://www.example.com/$1 [R=301,L]

Pattern

Flags Substitution

non-www to www RewriteEngine On RewriteCond %{HTTP_HOST} ^example\.com$ [NC] RewriteRule ^(.*)$ http://www.example.com/$1 [R=301,L]

Match this pattern Pattern inside parentheses is capture as variable ‘$1’

non-www to www RewriteEngine On RewriteCond %{HTTP_HOST} ^example\.com$ [NC] RewriteRule ^(.*)$ http://www.example.com/$1 [R=301,L]

Substitute it with “http://www.example.com”

non-www to www RewriteEngine On RewriteCond %{HTTP_HOST} ^example\.com$ [NC] RewriteRule ^(.*)$ http://www.example.com/$1 [R=301,L]

The pattern captured inside the parentheses

non-www to www RewriteEngine On RewriteCond %{HTTP_HOST} ^example\.com$ [NC] RewriteRule ^(.*)$ http://www.example.com/$1 [R=301,L]

Redirect with a 301 Code Make this the last RewriteRule

RewriteOptions inherit • •

Inherit the configuration of the parent

•

In per-directory context, conditions and rules of the parent directory's .htaccess configuration are inherited

In per-virtual-server context, maps, conditions and rules of the main server are inherited

Example in httpd.conf ...

RewriteRule ^(.*)$ index.php ...

ServerName zomgbacon.com DocumentRoot /home/bacon/public_html # Turn on the rewrite engine and inherit any rules RewriteEngine On RewriteOptions Inherit ...

RewriteBase URL-path • •

Sets the base URL for per-directory rewrites URLs are NOT directly related to physical filename paths

RewriteBase Example in .htaccess file # # # # #

/abc/def/.htaccess -- per-dir config file for directory /abc/def Remember: /abc/def is the physical path of /xyz, i.e., the server has a 'Alias /xyz /abc/def' directive e.g.

RewriteEngine On # let the server know that we were reached via /xyz and not # via the physical path prefix /abc/def RewriteBase /xyz # now the rewriting rules RewriteRule ^oldstuff\.html$

newstuff.html

RewriteLog log-path • • • •

Logs rewrites Level of logging can be tuned Relative paths are relative to DocumentRoot Absolute paths are...well, absolute.

RewriteLogLevel level • • • • •

Integer value 0-9 0 == disabled 9 == log nearly everything More verbose, greater impact on performance Higher levels == 2 or higher for debugging only

Logging Examples in httpd.conf

...

ServerName zomgbacon.com DocumentRoot /home/bacon/public_html # /home/bacon/public_html/rewrite.log RewriteLog rewrite.log # Make it semi-verbose RewriteLogLevel 5 # turn on rewrite engine and inherit rules RewriteEngine on RewriteOptions Inherit ...

fin