출처 : http://www.superuser.co.kr/home/lecture/?leccode=308 (원본에서 몇몇 수정 하였음)
Apache Rewrite Module -작성자 : 윤일-
Apache 는 추가적으로 사용할 수 있는 유용한 모듈들을 제공합니다.
이번강좌에서는 Apache의 URL Rewrite 모듈을 사용하기 위한 컴파일,설치 와 httpd.conf의 설정방법 그리고 활용방법에 대해 알아보겠습니다.
Apache 다운로드 : http://www.apache.org
1. rewrite 모듈을 사용하기 위한 Apache 컴파일옵션
[옵션] : --enable-rewrite
[설명] : Rewrite 모듈을 쓰기위한 Apache 컴파일 옵션은 --enable-rewrite 입니다. Configure 실행시에 --enable-rewrite 만 추가하시면 Apache에서 rewrite 모듈을 사용할 있게 됩니다. [예제]
[root@superuser root]# ./cofigure prefix=/usr/local/apache2 --enable-rewrite
[root@superuser root]# make
[root@superuser root]# make install
1. Rewrite 를 적용할 수 있는 범위
Rewrite 설정은 Server Config, Virtual Host, Directory, .htaccess 에 설정할 수 있습니다. 즉, Apache 서버 전체에 Global 설정과 특정 가상호스트에만 적용하도록 할수 있고 특정 디렉토리 에만 적용시킬수도 있습니다.
2. Rewrite 모듈 지시자
RewriteEngine [문법] : RewriteEngine On 또는 Off
[설명] : Rewriteing 엔진을 사용할지 여부를 설정합니다. 기본설정은 당연히 Off로 되어 있으며 RewriteEngine On 으로 설정하지 않는 이상 Rewritng 엔진을 활성화 시키지 않습니다.
[기타] : 현재 Apache에서 실행중인 모든 RewriteRule을 비활성화 시킬 때 RewriteRule 라인을 주석처리 하기보다 RewriteEngin Off 로 설정하는 것이 더 간편하고 올바른방법입니다.
RewreteLog [문법] : RewriteLog FILE-PATH
[설명] : RewriteLog 지시자는 Rewrite 엔진의 로그를 그록할 파일을 지정합니다. RewriteLog 파일을 항상 남기기 보다 잘못된 Rewrite 규칙들을 디버킹할 때 사용하기를 권장합니다. 아파치와 마찬가지로 RewriteLog 파일도 방문자수가 많은사이트에서는 감당못할 정도의 로그파일을 남기기 때문에 시스템 여유공간이 많이 없는 시스템에서는 해당 파티션의 하드사용률 100%로 인한 재앙(?)을 불러올수도 있습니다. [조건] : RewriteLog 지시자는 반드시 RewriteLogLevel 지시자와 함께 사용하여야 됩니다.
RewriteLogLevel [문법] : RewriteLogLevel Level
[설명] : RewriteLogLevel 지시자는 RewriteLog 지시자로 설정한 로그파일에 기록할 로그들에 대해 얼마나 자세한 내용을 로그로 남길것인가에 대해 설정하는 지시자입니다.
기록할 로그 Level 은 0~9까지 사용할 수 있으며 0은 로그를 기록하지 않겠다는 의미입니다. Level 숫자가 높을수록 자세한 로그를 기록합니다
RewriteCond [문법] : RewriteCond TestStirng CondPattern [설명] : RewriteCond 지시자는 RewriteRule 과 함께 사용되는 규칙으로 RewriteCond 다음에 오는 RewriteRule은 RewrieteCond 에서 설정한 패턴과 일치해야지만 RewriteRule들을 실행한다.
RewriteRule [문법] : RewriteRule Pattern Substitution
[설명] : Rewrite 모듈의 실질적인 Rewrite 규칙들을 적용하는 지시자입니다. Pattern(Input URL) 을 Subtitution(Return URL)로 변경하기 위한 모든 규칙들은 이 지시자를 사용해서 설정해야 됩니다.
[기타] : Pattern(Input URL) 에는 Perl 정규표현식을 사용할수 있기 때문에 Input URL 의 규칙을 유연하게 적용할 수 있습니다.
[표1] : 정규표현식 기초
. | 다수의 한문자 | ? | 0개 이상의 한문자 | * | 0개 이상의 문자 또는 문자열 | + | 1개 이상의 문자 또는 문자열 | (chars) | (, ) 안의 문자또는 문자열을 그룹으로 묶습니다. 이 문자그룹은 Substitution(return URL)에서 $N 의 변수로 활용할수 있습니니다. | ^ | 문자열의 첫문(열)을 지정합니다. | $ | 문자열의 끝 문자(열)을 지정합니다. | \(역슬래쉬) | 정규표현식에서 특별한 의미로 사용되는 문자의 특수기능을 제거합니다.(예:(, ), [, ] . 등) | {n} | 정확히 n번 반복 | {n,} | n번 이상 반복 | {n,m} | n 이상 m 이하 반복 | [chars] | 문자들의 범위 또는 표현할 수 있는 문자들을 설정합니다. 예) [a-z] : a 부터 z 까지의 소문자, [tT] : 소문자 t 또는 대문자 T |
[표2] : 정규표현식 단축표현들
[:alpha:] | 알파벳. [a-zA-Z] 와 같은 표현 | [:alnum:] | 알파벳과 숫자. [a-zA-Z0-9] 와 같은 표현 | [:digit:] | 숫자 [0-9] 와 같은 표현 | [:upper:] | 대문자. [A-Z] 와 같은 표현 |
RewriteRule 플래그
forbidden|F
[설명] : 요청하는 페이지를 403 에러로 redirect 시킵니다. RedirectRule 이 적용되고 있는 페이지를 일시적으로 사용중단을 시키거나 사용자로 하여금 페이지 접근을 할수 없게 할 때 사용합니다.
[예제] : RewriteRule ^/test /home/blog/html/test.php [F]
사용자가 /test 로 접근할 경우 403 에러를 보냅니다.
gone|G
[설명] : 요청하는 페이지를 410 에러로 redirect 시킵니다. 410 에러는 페이지가 사라젔거나 존재하지 않는다는 메시지입니다. 이것도 forbidden 과 마찬가지로 RedirectRule 이 적용되던 페이지를 일시적으로 중단시킬 때 유용하게 사용할 수 있습니다.
last|L
[설명] : 이 플래그가 적용되면 뒤에 어떤 룰이 있더라도 이룰 아래의 규칙들은 적용되지 않고 RewriteRule 을 빠져나가게 됩니다. C, Perl, PHP 프로그램에서 루프를 빠져나가는 break 와 같은 의미를 가집니다.
chain|C [설명] : 이 플래그의 결과를 다음 RewriteRule 의 input 값으로 사용합니다. [기타] : 이 룰은 사용자 홈의 도메인을 2차 도메인으로 자동설정해 줄 때 많이 쓰는 룰입니다. RewriteRule의 input은 도메인을 제외한 URI 를 인식하기 때문에 도메인까지 인식을 시켜 서 다음 RewriteRule 로 체크를 하기 위해 사용한 것입니다. 즉, http://user_id.domain.com/hello.html 이란 요청이 들어오면 /home/user_id/public_html/hello.html 로 redirect 시켜줍니다. 위와 같이 2차 도메인을 이용해 계정 사용자의 홈을 지정하기 위해서는 DNS 세팅이 선행되어야 됩니다. [예제1] : RewriteRule ^(.+) %{HTTP_HOST}$1 [C] RewriteRule ^([^.]+)\.domain\.com(.*) /home/$1/public_html$2 [예제2] : RwriteRule 설정예 1. http://yourdomain.com/user_id -> http://yourdomain.com/home.php?id=user_id RewriteRule ^/([a-zA-Z0-9])$ /home/user_id/public_html/home.php?id=$1
설명 : 도메인(http://yourdomain.com) 뒤에 오는 영문숫자로된 문자열을 지정하면서 그룹으 로 묶었습니다. 이렇게 그룹으로 설정된 문자열 Pattern 은 Substitution(return URL) 에서 $1 이라는 변수로 받아 사용하게 됩니다. 즉 http://yourdomain.com/superuser 라는 페이지 요청이 들어오면 실제로는 http://yourdomain.com/home.php?id=superuser 라는 페이지로 redirect 시켜줍니다. 블로그나 카페(동호회) 사이트에서 블로그 사용자의 ID 로 개인 블로그 주소를 부여할 때 http://blog.com/user_id 로 부여해 주지만 실제 실행되는 파일은 이와 같이 redirect 시켜주는 경우가 많습니다. 2. http://yourdomain.com/daum -> http://www.daum.net
RewriteRule ^/daum$ -> http://www.daum.net
[설명] : http://yourdomain.com/daum 라는 페이지 요청이 들어오면 도메인이 다른
http://www.daum.net 이라는 페이지로 redirect 시켜줍니다.
RewriteOptions [문법] : RewriteOptions Options
[설명] : 현재 사용할 수 있는 option 은 MaxRedirects=number 를 사용할 수 있으며 설정된 number값에 도달하게 되면 500 Internal Server Error 를 남기고 RewriteRule을 종료합니 다. 잘못된 RewriteRule에 의한 무한 루프를 방지하기 위한 목적으로 사용되는데 시스템 이 이유없이 다운된다거나 할 때 이 옵션과 Log 기록을 참고하여 디버깅 및 시스템 다운 을 방지할 수 있습니다. 이 지사자는 Apache 2.0.45 이상에서 사용할 수 있습니다.
3. 실제 적용예
가상호스트 www.superuser.co.kr 에 대해 Rewrite Rule을 적용한 예입니다. 이 부분은 실제 운영
되는 블로그 사이트를 위해 RewriteRule 을 적용한 예입니다.
DocumentRoot /home/blog/html
ServerName blog.xxx.ac.kr # 여기까지는 일반적인 가상호스트 설정입니다.
RewriteEngine on
# RewriteRule을 사용하기 위해 On 으로 설정합니다.
RewriteLog /home/blog/rewrite_log_admin3.log
RewriteLogLevel 9
# Rewrite 실행중 Log를 남기기 위해 로그파일과 로그레벨을 지정했습니다.
RewriteRule ^/tb/([a-zA-Z0-9]+)/([0-9]+)$ /home/blog/html/blog/trackback.php?id=$1&post_no=$2 # 위설정은 블로그에 등록된 포스트의 트랙백 주소를 부여하기 위해 설정한 RewriteRule 로써 Pattern에 두개의 그룹이 존재하고 return URL에 순서대로 각 그룹을 $1 과 $2 로 받아 GET 변수로 치환한것입니다.
RewriteRule ^/xml/([a-zA-Z0-9]+)$ /home/blog/html/blog/rss_feed.php?id=$1
# 각블로그별 RSS 주소를 실제 파일로 지정한것입니다.
RewriteCond %{REQUEST_URI} !^/admin$
RewriteRule ^/([a-zA-Z0-9]+)$ /home/blog/html/blog/main.php?id=$1
# 먼저 RewriteCond 로 실제 존재하는 admin 이라는 디렉토리를 이어지는 RewriteRule에서 제외시키고 http://domain.com/user_id 로의 요청을 모두 /home/blog/html/blog/main.php?id=user_id로 redirect 시키는 룰입니다.
RewriteRule ^/([a-zA-Z0-9]+)/([0-9]+)$ /home/blog/html/blog/main.php?id=$1&post_no=$2
# /user_id/1345 로 요청하는 페이지를 /home/blog/html/blog/main.php?id=user_id&post_no=1345 로 redirect 시키는 룰입니다.
4. 마치면서
위에서 언급한 RewriteRule 뿐만 아니라 여러가지 상황에서 RewriteRule을 잘 활용한다면 아주 유용하게 웹페이지를 컨트롤 할수 있습니다. RewriteRule 을 세팅하기 이전에 반드시 정규표헌식에 대해 어느정도 공부한후 적용해 보실 것을 권합니다.
---------------------------------------------------------------------------------------- ![[APACHE DOCUMENTATION]](http://httpd.apache.org/docs/1.3/images/sub.gif) Apache HTTP Server Version 1.3Is this the version you want? For more recent versions, check our documentation index.
Module mod_rewrite
URL Rewriting EngineThis module provides a rule-based rewriting engine to rewrite requested URLs on the fly. Status: Extension
Source File: mod_rewrite.c
Module Identifier: rewrite_module
Compatibility: Available in Apache 1.2 and later.
Summary``The great thing about mod_rewrite is it gives you all the configurability and flexibility of Sendmail. The downside to mod_rewrite is that it gives you all the configurability and flexibility of Sendmail.'' -- Brian Behlendorf
Apache Group
`` Despite the tons of examples and docs, mod_rewrite is voodoo. Damned cool voodoo, but still voodoo. '' -- Brian Moore
bem@news.cmc.net
Welcome to mod_rewrite, the Swiss Army Knife of URL manipulation! This module uses a rule-based rewriting engine (based on a regular-expression parser) to rewrite requested URLs on the fly. It supports an unlimited number of rules and an unlimited number of attached rule conditions for each rule to provide a really flexible and powerful URL manipulation mechanism. The URL manipulations can depend on various tests, for instance server variables, environment variables, HTTP headers, time stamps and even external database lookups in various formats can be used to achieve a really granular URL matching. This module operates on the full URLs (including the path-info part) both in per-server context (httpd.conf) and per-directory context (.htaccess) and can even generate query-string parts on result. The rewritten result can lead to internal sub-processing, external request redirection or even to an internal proxy throughput. But all this functionality and flexibility has its drawback: complexity. So don't expect to understand this entire module in just one day. This module was invented and originally written in April 1996
and gifted exclusively to the The Apache Group in July 1997 by Ralf S. Engelschall
rse@engelschall.com
www.engelschall.com
Table Of ContentsInternal Processing Configuration Directives Miscellaneous
The internal processing of this module is very complex but needs to be explained once even to the average user to avoid common mistakes and to let you exploit its full functionality. First you have to understand that when Apache processes a HTTP request it does this in phases. A hook for each of these phases is provided by the Apache API. Mod_rewrite uses two of these hooks: the URL-to-filename translation hook which is used after the HTTP request has been read but before any authorization starts and the Fixup hook which is triggered after the authorization phases and after the per-directory config files (.htaccess) have been read, but before the content handler is activated. So, after a request comes in and Apache has determined the corresponding server (or virtual server) the rewriting engine starts processing of all mod_rewrite directives from the per-server configuration in the URL-to-filename phase. A few steps later when the final data directories are found, the per-directory configuration directives of mod_rewrite are triggered in the Fixup phase. In both situations mod_rewrite rewrites URLs either to new URLs or to filenames, although there is no obvious distinction between them. This is a usage of the API which was not intended to be this way when the API was designed, but as of Apache 1.x this is the only way mod_rewrite can operate. To make this point more clear remember the following two points: - Although mod_rewrite rewrites URLs to URLs, URLs to filenames and even filenames to filenames, the API currently provides only a URL-to-filename hook. In Apache 2.0 the two missing hooks will be added to make the processing more clear. But this point has no drawbacks for the user, it is just a fact which should be remembered: Apache does more in the URL-to-filename hook than the API intends for it.
- Unbelievably mod_rewrite provides URL manipulations in per-directory context, i.e., within
.htaccess files, although these are reached a very long time after the URLs have been translated to filenames. It has to be this way because .htaccess files live in the filesystem, so processing has already reached this stage. In other words: According to the API phases at this time it is too late for any URL manipulations. To overcome this chicken and egg problem mod_rewrite uses a trick: When you manipulate a URL/filename in per-directory context mod_rewrite first rewrites the filename back to its corresponding URL (which is usually impossible, but see the RewriteBase directive below for the trick to achieve this) and then initiates a new internal sub-request with the new URL. This restarts processing of the API phases. Again mod_rewrite tries hard to make this complicated step totally transparent to the user, but you should remember here: While URL manipulations in per-server context are really fast and efficient, per-directory rewrites are slow and inefficient due to this chicken and egg problem. But on the other hand this is the only way mod_rewrite can provide (locally restricted) URL manipulations to the average user.
Don't forget these two points! Now when mod_rewrite is triggered in these two API phases, it reads the configured rulesets from its configuration structure (which itself was either created on startup for per-server context or during the directory walk of the Apache kernel for per-directory context). Then the URL rewriting engine is started with the contained ruleset (one or more rules together with their conditions). The operation of the URL rewriting engine itself is exactly the same for both configuration contexts. Only the final result processing is different. The order of rules in the ruleset is important because the rewriting engine processes them in a special (and not very obvious) order. The rule is this: The rewriting engine loops through the ruleset rule by rule (RewriteRule directives) and when a particular rule matches it optionally loops through existing corresponding conditions (RewriteCond directives). For historical reasons the conditions are given first, and so the control flow is a little bit long-winded. See Figure 1 for more details. | | Figure 1: The control flow through the rewriting ruleset |
As you can see, first the URL is matched against the Pattern of each rule. When it fails mod_rewrite immediately stops processing this rule and continues with the next rule. If the Pattern matches, mod_rewrite looks for corresponding rule conditions. If none are present, it just substitutes the URL with a new value which is constructed from the string Substitution and goes on with its rule-looping. But if conditions exist, it starts an inner loop for processing them in the order that they are listed. For conditions the logic is different: we don't match a pattern against the current URL. Instead we first create a string TestString by expanding variables, back-references, map lookups, etc. and then we try to match CondPattern against it. If the pattern doesn't match, the complete set of conditions and the corresponding rule fails. If the pattern matches, then the next condition is processed until no more conditions are available. If all conditions match, processing is continued with the substitution of the URL with Substitution. As of Apache 1.3.20, special characters in TestString and Substitution strings can be escaped (that is, treated as normal characters without their usual special meaning) by prefixing them with a slosh ('\') character. In other words, you can include an actual dollar-sign character in a Substitution string by using '\$'; this keeps mod_rewrite from trying to treat it as a backreference. One important thing here has to be remembered: Whenever you use parentheses in Pattern or in one of the CondPattern, back-references are internally created which can be used with the strings $N and %N (see below). These are available for creating the strings Substitution and TestString. Figure 2 shows to which locations the back-references are transfered for expansion. ![[Needs graphics capability to display]](http://httpd.apache.org/docs/1.3/images/mod_rewrite_fig2.gif) | | Figure 2: The back-reference flow through a rule |
We know this was a crash course on mod_rewrite's internal processing. But you will benefit from this knowledge when reading the following documentation of the available directives.
Syntax: RewriteEngine on|off
Default: RewriteEngine off
Context: server config, virtual host, directory, .htaccess
Override: FileInfo
Status: Extension
Module: mod_rewrite.c
Compatibility: Apache 1.2
The RewriteEngine directive enables or disables the runtime rewriting engine. If it is set to off this module does no runtime processing at all. It does not even update the SCRIPT_URx environment variables. Use this directive to disable the module instead of commenting out all the RewriteRule directives! Note that, by default, rewrite configurations are not inherited. This means that you need to have a RewriteEngine on directive for each virtual host in which you wish to use it.
Syntax: RewriteOptions Option
Default: RewriteOptions MaxRedirects=10
Context: server config, virtual host, directory, .htaccess
Override: FileInfo
Status: Extension
Module: mod_rewrite.c
Compatibility: Apache 1.2; MaxRedirects is available in Apache 1.3.28 and later
The RewriteOptions directive sets some special options for the current per-server or per-directory configuration. The Option strings can be one of the following: inherit - This forces the current configuration to inherit the configuration of the parent. In per-virtual-server context this means that the maps, conditions and rules of the main server are inherited. In per-directory context this means that conditions and rules of the parent directory's
.htaccess configuration are inherited. MaxRedirects=number - In order to prevent endless loops of internal redirects issued by per-directory
RewriteRules, mod_rewrite aborts the request after reaching a maximum number of such redirects and responds with an 500 Internal Server Error. If you really need more internal redirects than 10 per request, you may increase the default to the desired value.
Syntax: RewriteLog file-path
Default: None
Context: server config, virtual host
Override: Not applicable
Status: Extension
Module: mod_rewrite.c
Compatibility: Apache 1.2
The RewriteLog directive sets the name of the file to which the server logs any rewriting actions it performs. If the name does not begin with a slash ('/') then it is assumed to be relative to the Server Root. The directive should occur only once per server config. Note: To disable the logging of rewriting actions it is not recommended to set file-path to /dev/null, because although the rewriting engine does not then output to a logfile it still creates the logfile output internally. This will slow down the server with no advantage to the administrator! To disable logging either remove or comment out the RewriteLog directive or use RewriteLogLevel 0! |
| Security: See the Apache Security Tips document for details on why your security could be compromised if the directory where logfiles are stored is writable by anyone other than the user that starts the server. |
Example: RewriteLog "/usr/local/var/apache/logs/rewrite.log"
Syntax: RewriteLogLevel Level
Default: RewriteLogLevel 0
Context: server config, virtual host
Override: Not applicable
Status: Extension
Module: mod_rewrite.c
Compatibility: Apache 1.2
The RewriteLogLevel directive sets the verbosity level of the rewriting logfile. The default level 0 means no logging, while 9 or more means that practically all actions are logged. To disable the logging of rewriting actions simply set Level to 0. This disables all rewrite action logs. | Notice: Using a high value for Level will slow down your Apache server dramatically! Use the rewriting logfile at a Level greater than 2 only for debugging! |
Example: RewriteLogLevel 3
Syntax: RewriteLock file-path
Default: None
Context: server config
Override: Not applicable
Status: Extension
Module: mod_rewrite.c
Compatibility: Apache 1.3
This directive sets the filename for a synchronization lockfile which mod_rewrite needs to communicate with RewriteMap programs. Set this lockfile to a local path (not on a NFS-mounted device) when you want to use a rewriting map-program. It is not required for other types of rewriting maps.
Syntax: RewriteMap MapName MapType:MapSource
Default: not used per default
Context: server config, virtual host
Override: Not applicable
Status: Extension
Module: mod_rewrite.c
Compatibility: Apache 1.2 (partially), Apache 1.3
The RewriteMap directive defines a Rewriting Map which can be used inside rule substitution strings by the mapping-functions to insert/substitute fields through a key lookup. The source of this lookup can be of various types. The MapName is the name of the map and will be used to specify a mapping-function for the substitution strings of a rewriting rule via one of the following constructs: ${ MapName : LookupKey }
${ MapName : LookupKey | DefaultValue }
When such a construct occurs the map MapName is consulted and the key LookupKey is looked-up. If the key is found, the map-function construct is substituted by SubstValue. If the key is not found then it is substituted by DefaultValue or by the empty string if no DefaultValue was specified. The following combinations for MapType and MapSource can be used: - Standard Plain Text
MapType: txt, MapSource: Unix filesystem path to valid regular file This is the standard rewriting map feature where the MapSource is a plain ASCII file containing either blank lines, comment lines (starting with a '#' character) or pairs like the following - one per line. MatchingKey SubstValue Example: #### map.txt -- rewriting map##Ralf.S.Engelschall rse # Bastard Operator From HellMr.Joe.Average joe # Mr. Average |
RewriteMap real-to-user txt:/path/to/file/map.txt |
- Randomized Plain Text
MapType: rnd, MapSource: Unix filesystem path to valid regular file This is identical to the Standard Plain Text variant above but with a special post-processing feature: After looking up a value it is parsed according to contained ``|'' characters which have the meaning of ``or''. In other words they indicate a set of alternatives from which the actual returned value is chosen randomly. Although this sounds crazy and useless, it was actually designed for load balancing in a reverse proxy situation where the looked up values are server names. Example: #### map.txt -- rewriting map##static www1|www2|www3|www4dynamic www5|www6 |
RewriteMap servers rnd:/path/to/file/map.txt |
- Hash File
MapType: dbm, MapSource: Unix filesystem path to valid regular file Here the source is a binary NDBM format file containing the same contents as a Plain Text format file, but in a special representation which is optimized for really fast lookups. You can create such a file with any NDBM tool or with the following Perl script: #!/path/to/bin/perl#### txt2dbm -- convert txt map to dbm format##use NDBM_File;use Fcntl;($txtmap, $dbmmap) = @ARGV;open(TXT, "<$txtmap") or die "Couldn't open $txtmap!\n";tie (%DB, 'NDBM_File', $dbmmap,O_RDWR|O_TRUNC|O_CREAT, 0644) or die "Couldn't create $dbmmap!\n";while (<TXT>) { next if (/^\s*#/ or /^\s*$/); $DB{$1} = $2 if (/^\s*(\S+)\s+(\S+)/);}untie %DB;close(TXT); |
- Internal Function
MapType: int, MapSource: Internal Apache function Here the source is an internal Apache function. Currently you cannot create your own, but the following functions already exists: - toupper:
Converts the looked up key to all upper case. - tolower:
Converts the looked up key to all lower case. - escape:
Translates special characters in the looked up key to hex-encodings. - unescape:
Translates hex-encodings in the looked up key back to special characters.
- External Rewriting Program
MapType: prg, MapSource: Unix filesystem path to valid regular file Here the source is a program, not a map file. To create it you can use the language of your choice, but the result has to be a executable (i.e., either object-code or a script with the magic cookie trick '#!/path/to/interpreter' as the first line). This program is started once at startup of the Apache servers and then communicates with the rewriting engine over its stdin and stdout file-handles. For each map-function lookup it will receive the key to lookup as a newline-terminated string on stdin. It then has to give back the looked-up value as a newline-terminated string on stdout or the four-character string ``NULL'' if it fails (i.e., there is no corresponding value for the given key). A trivial program which will implement a 1:1 map (i.e., key == value) could be: #!/usr/bin/perl$| = 1;while (<STDIN>) { # ...put here any transformations or lookups... print $_;} |
But be very careful:
- ``Keep it simple, stupid'' (KISS), because if this program hangs it will hang the Apache server when the rule occurs.
- Avoid one common mistake: never do buffered I/O on
stdout! This will cause a deadloop! Hence the ``$|=1'' in the above example... - Use the RewriteLock directive to define a lockfile mod_rewrite can use to synchronize the communication to the program. By default no such synchronization takes place.
The RewriteMap directive can occur more than once. For each mapping-function use one RewriteMap directive to declare its rewriting mapfile. While you cannot declare a map in per-directory context it is of course possible to use this map in per-directory context. Note: For plain text and DBM format files the looked-up keys are cached in-core until the mtime of the mapfile changes or the server does a restart. This way you can have map-functions in rules which are used for every request. This is no problem, because the external lookup only happens once! |
Syntax: RewriteBase URL-path
Default: default is the physical directory path
Context: directory, .htaccess
Override: FileInfo
Status: Extension
Module: mod_rewrite.c
Compatibility: Apache 1.2
The RewriteBase directive explicitly sets the base URL for per-directory rewrites. As you will see below, RewriteRule can be used in per-directory config files (.htaccess). There it will act locally, i.e., the local directory prefix is stripped at this stage of processing and your rewriting rules act only on the remainder. At the end it is automatically added back to the path. When a substitution occurs for a new URL, this module has to re-inject the URL into the server processing. To be able to do this it needs to know what the corresponding URL-prefix or URL-base is. By default this prefix is the corresponding filepath itself. But at most websites URLs are NOT directly related to physical filename paths, so this assumption will usually be wrong! There you have to use the RewriteBase directive to specify the correct URL-prefix. Notice: If your webserver's URLs are not directly related to physical file paths, you have to use RewriteBase in every .htaccess files where you want to use RewriteRule directives. |
Example: Assume the following per-directory config 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/defRewriteBase /xyz# now the rewriting rulesRewriteRule ^oldstuff\.html$ newstuff.html |
In the above example, a request to /xyz/oldstuff.html gets correctly rewritten to the physical file /abc/def/newstuff.html. Note - For Apache hackers:
The following list gives detailed information about the internal processing steps: Request: /xyz/oldstuff.htmlInternal Processing: /xyz/oldstuff.html -> /abc/def/oldstuff.html (per-server Alias) /abc/def/oldstuff.html -> /abc/def/newstuff.html (per-dir RewriteRule) /abc/def/newstuff.html -> /xyz/newstuff.html (per-dir RewriteBase) /xyz/newstuff.html -> /abc/def/newstuff.html (per-server Alias)Result: /abc/def/newstuff.html This seems very complicated but is the correct Apache internal processing, because the per-directory rewriting comes too late in the process. So, when it occurs the (rewritten) request has to be re-injected into the Apache kernel! BUT: While this seems like a serious overhead, it really isn't, because this re-injection happens fully internally to the Apache server and the same procedure is used by many other operations inside Apache. So, you can be sure the design and implementation is correct. |
Syntax: RewriteCond TestString CondPattern
Default: None
Context: server config, virtual host, directory, .htaccess
Override: FileInfo
Status: Extension
Module: mod_rewrite.c
Compatibility: Apache 1.2 (partially), Apache 1.3
The RewriteCond directive defines a rule condition. Precede a RewriteRule directive with one or more RewriteCond directives. The following rewriting rule is only used if its pattern matches the current state of the URI and if these additional conditions apply too. TestString is a string which can contains the following expanded constructs in addition to plain text: - RewriteRule backreferences: These are backreferences of the form
$N
(0 <= N <= 9) which provide access to the grouped parts (parenthesis!) of the pattern from the corresponding RewriteRule directive (the one following the current bunch of RewriteCond directives). - RewriteCond backreferences: These are backreferences of the form
%N
(1 <= N <= 9) which provide access to the grouped parts (parentheses!) of the pattern from the last matched RewriteCond directive in the current bunch of conditions. - RewriteMap expansions: These are expansions of the form
${mapname:key|default}
See the documentation for RewriteMap for more details. - Server-Variables: These are variables of the form
%{ NAME_OF_VARIABLE }
where NAME_OF_VARIABLE can be a string taken from the following list: | HTTP headers: HTTP_USER_AGENT
HTTP_REFERER
HTTP_COOKIE
HTTP_FORWARDED
HTTP_HOST
HTTP_PROXY_CONNECTION
HTTP_ACCEPT
| connection & request: REMOTE_ADDR
REMOTE_HOST
REMOTE_USER
REMOTE_IDENT
REQUEST_METHOD
SCRIPT_FILENAME
PATH_INFO
QUERY_STRING
AUTH_TYPE
| | server internals: DOCUMENT_ROOT
SERVER_ADMIN
SERVER_NAME
SERVER_ADDR
SERVER_PORT
SERVER_PROTOCOL
SERVER_SOFTWARE
| system stuff: TIME_YEAR
TIME_MON
TIME_DAY
TIME_HOUR
TIME_MIN
TIME_SEC
TIME_WDAY
TIME
| specials: API_VERSION
THE_REQUEST
REQUEST_URI
REQUEST_FILENAME
IS_SUBREQ
|
Notice: These variables all correspond to the similarly named HTTP MIME-headers, C variables of the Apache server or struct tm fields of the Unix system. Most are documented elsewhere in the Manual or in the CGI specification. Those that are special to mod_rewrite include: IS_SUBREQ - Will contain the text "true" if the request currently being processed is a sub-request, "false" otherwise. Sub-requests may be generated by modules that need to resolve additional files or URIs in order to complete their tasks.
API_VERSION - This is the version of the Apache module API (the internal interface between server and module) in the current httpd build, as defined in include/ap_mmn.h. The module API version corresponds to the version of Apache in use (in the release version of Apache 1.3.14, for instance, it is 19990320:10), but is mainly of interest to module authors.
THE_REQUEST - The full HTTP request line sent by the browser to the server (e.g., "
GET /index.html HTTP/1.1"). This does not include any additional headers sent by the browser. REQUEST_URI - The resource requested in the HTTP request line. (In the example above, this would be "/index.html".)
REQUEST_FILENAME - The full local filesystem path to the file or script matching the request.
|
Special Notes: - The variables SCRIPT_FILENAME and REQUEST_FILENAME contain the same value, i.e., the value of the
filename field of the internal request_rec structure of the Apache server. The first name is just the commonly known CGI variable name while the second is the consistent counterpart to REQUEST_URI (which contains the value of the uri field of request_rec). - There is the special format:
%{ENV:variable} where variable can be any environment variable. This is looked-up via internal Apache structures and (if not found there) via getenv() from the Apache server process. - There is the special format:
%{HTTP:header} where header can be any HTTP MIME-header name. This is looked-up from the HTTP request. Example: %{HTTP:Proxy-Connection} is the value of the HTTP header ``Proxy-Connection:''. - There is the special format
%{LA-U:variable} for look-aheads which perform an internal (URL-based) sub-request to determine the final value of variable. Use this when you want to use a variable for rewriting which is actually set later in an API phase and thus is not available at the current stage. For instance when you want to rewrite according to the REMOTE_USER variable from within the per-server context (httpd.conf file) you have to use %{LA-U:REMOTE_USER} because this variable is set by the authorization phases which come after the URL translation phase where mod_rewrite operates. On the other hand, because mod_rewrite implements its per-directory context (.htaccess file) via the Fixup phase of the API and because the authorization phases come before this phase, you just can use %{REMOTE_USER} there. - There is the special format:
%{LA-F:variable} which performs an internal (filename-based) sub-request to determine the final value of variable. Most of the time this is the same as LA-U above.
CondPattern is the condition pattern, i.e., a regular expression which is applied to the current instance of the TestString, i.e., TestString is evaluated and then matched against CondPattern. Remember: CondPattern is a standard Extended Regular Expression with some additions: - You can prefix the pattern string with a '
!' character (exclamation mark) to specify a non-matching pattern. - There are some special variants of CondPatterns. Instead of real regular expression strings you can also use one of the following:
- '<CondPattern' (is lexically lower)
Treats the CondPattern as a plain string and compares it lexically to TestString. True if TestString is lexically lower than CondPattern. - '>CondPattern' (is lexically greater)
Treats the CondPattern as a plain string and compares it lexically to TestString. True if TestString is lexically greater than CondPattern. - '=CondPattern' (is lexically equal)
Treats the CondPattern as a plain string and compares it lexically to TestString. True if TestString is lexically equal to CondPattern, i.e the two strings are exactly equal (character by character). If CondPattern is just "" (two quotation marks) this compares TestString to the empty string. - '-d' (is directory)
Treats the TestString as a pathname and tests if it exists and is a directory. - '-f' (is regular file)
Treats the TestString as a pathname and tests if it exists and is a regular file. - '-s' (is regular file with size)
Treats the TestString as a pathname and tests if it exists and is a regular file with size greater than zero. - '-l' (is symbolic link)
Treats the TestString as a pathname and tests if it exists and is a symbolic link. - '-F' (is existing file via subrequest)
Checks if TestString is a valid file and accessible via all the server's currently-configured access controls for that path. This uses an internal subrequest to determine the check, so use it with care because it decreases your servers performance! - '-U' (is existing URL via subrequest)
Checks if TestString is a valid URL and accessible via all the server's currently-configured access controls for that path. This uses an internal subrequest to determine the check, so use it with care because it decreases your server's performance!
| Notice: All of these tests can also be prefixed by an exclamation mark ('!') to negate their meaning. |
Additionally you can set special flags for CondPattern by appending [flags]
as the third argument to the RewriteCond directive. Flags is a comma-separated list of the following flags: - '
nocase|NC' (no case)
This makes the test case-insensitive, i.e., there is no difference between 'A-Z' and 'a-z' both in the expanded TestString and the CondPattern. This flag is effective only for comparisons between TestString and CondPattern. It has no effect on filesystem and subrequest checks. - '
ornext|OR' (or next condition)
Use this to combine rule conditions with a local OR instead of the implicit AND. Typical example: RewriteCond %{REMOTE_HOST} ^host1.* [OR]RewriteCond %{REMOTE_HOST} ^host2.* [OR]RewriteCond %{REMOTE_HOST} ^host3.*RewriteRule ...some special stuff for any of these hosts...
Without this flag you would have to write the cond/rule three times.
Example: To rewrite the Homepage of a site according to the ``User-Agent:'' header of the request, you can use the following: RewriteCond %{HTTP_USER_AGENT} ^Mozilla.*RewriteRule ^/$ /homepage.max.html [L]RewriteCond %{HTTP_USER_AGENT} ^Lynx.*RewriteRule ^/$ /homepage.min.html [L]RewriteRule ^/$ /homepage.std.html [L]
Interpretation: If you use Netscape Navigator as your browser (which identifies itself as 'Mozilla'), then you get the max homepage, which includes Frames, etc. If you use the Lynx browser (which is Terminal-based), then you get the min homepage, which contains no images, no tables, etc. If you use any other browser you get the standard homepage.
Syntax: RewriteRule Pattern Substitution
Default: None
Context: server config, virtual host, directory, .htaccess
Override: FileInfo
Status: Extension
Module: mod_rewrite.c
Compatibility: Apache 1.2 (partially), Apache 1.3
The RewriteRule directive is the real rewriting workhorse. The directive can occur more than once. Each directive then defines one single rewriting rule. The definition order of these rules is important, because this order is used when applying the rules at run-time. Pattern can be (for Apache 1.1.x a System V8 and for Apache 1.2.x and later a POSIX) regular expression which gets applied to the current URL. Here ``current'' means the value of the URL when this rule gets applied. This may not be the originally requested URL, because any number of rules may already have matched and made alterations to it. Some hints about the syntax of regular expressions: Text: . Any single character [chars] Character class: One of chars [^chars] Character class: None of chars text1|text2 Alternative: text1 or text2Quantifiers: ? 0 or 1 of the preceding text * 0 or N of the preceding text (N > 0) + 1 or N of the preceding text (N > 1)Grouping: (text) Grouping of text (either to set the borders of an alternative or for making backreferences where the Nth group can be used on the RHS of a RewriteRule with $N)Anchors: ^ Start of line anchor $ End of line anchorEscaping: \char escape that particular char (for instance to specify the chars ".[]()" etc.) |
For more information about regular expressions either have a look at your local regex(3) manpage or its src/regex/regex.3 copy in the Apache 1.3 distribution. If you are interested in more detailed information about regular expressions and their variants (POSIX regex, Perl regex, etc.) have a look at the following dedicated book on this topic: Mastering Regular Expressions
Jeffrey E.F. Friedl
Nutshell Handbook Series
O'Reilly & Associates, Inc. 1997
ISBN 1-56592-257-3
Additionally in mod_rewrite the NOT character ('!') is a possible pattern prefix. This gives you the ability to negate a pattern; to say, for instance: ``if the current URL does NOT match this pattern''. This can be used for exceptional cases, where it is easier to match the negative pattern, or as a last default rule. Notice: When using the NOT character to negate a pattern you cannot have grouped wildcard parts in the pattern. This is impossible because when the pattern does NOT match, there are no contents for the groups. In consequence, if negated patterns are used, you cannot use $N in the substitution string! |
Substitution of a rewriting rule is the string which is substituted for (or replaces) the original URL for which Pattern matched. Beside plain text you can use - back-references
$N to the RewriteRule pattern - back-references
%N to the last matched RewriteCond pattern - server-variables as in rule condition test-strings (
%{VARNAME}) - mapping-function calls (
${mapname:key|default})
Back-references are $N (N=0..9) identifiers which will be replaced by the contents of the Nth group of the matched Pattern. The server-variables are the same as for the TestString of a RewriteCond directive. The mapping-functions come from the RewriteMap directive and are explained there. These three types of variables are expanded in the order of the above list. As already mentioned above, all the rewriting rules are applied to the Substitution (in the order of definition in the config file). The URL is completely replaced by the Substitution and the rewriting process goes on until there are no more rules unless explicitly terminated by a L flag - see below. There is a special substitution string named '-' which means: NO substitution! Sounds silly? No, it is useful to provide rewriting rules which only match some URLs but do no substitution, e.g., in conjunction with the C (chain) flag to be able to have more than one pattern to be applied before a substitution occurs. One more note: You can even create URLs in the substitution string containing a query string part. Just use a question mark inside the substitution string to indicate that the following stuff should be re-injected into the QUERY_STRING. When you want to erase an existing query string, end the substitution string with just the question mark. Note: There is a special feature: When you prefix a substitution field with http://thishost[:thisport] then mod_rewrite automatically strips it out. This auto-reduction on implicit external redirect URLs is a useful and important feature when used in combination with a mapping-function which generates the hostname part. Have a look at the first example in the example section below to understand this. |
Remember: An unconditional external redirect to your own server will not work with the prefix http://thishost because of this feature. To achieve such a self-redirect, you have to use the R-flag (see below). |
Additionally you can set special flags for Substitution by appending [flags]
as the third argument to the RewriteRule directive. Flags is a comma-separated list of the following flags: - '
redirect|R [=code]' (force redirect)
Prefix Substitution with http://thishost[:thisport]/ (which makes the new URL a URI) to force a external redirection. If no code is given a HTTP response of 302 (MOVED TEMPORARILY) is used. If you want to use other response codes in the range 300-400 just specify them as a number or use one of the following symbolic names: temp (default), permanent, seeother. Use it for rules which should canonicalize the URL and give it back to the client, e.g., translate ``/~'' into ``/u/'' or always append a slash to /u/user, etc.
Note: When you use this flag, make sure that the substitution field is a valid URL! If not, you are redirecting to an invalid location! And remember that this flag itself only prefixes the URL with http://thishost[:thisport]/, rewriting continues. Usually you also want to stop and do the redirection immediately. To stop the rewriting you also have to provide the 'L' flag. - '
forbidden|F' (force URL to be forbidden)
This forces the current URL to be forbidden, i.e., it immediately sends back a HTTP response of 403 (FORBIDDEN). Use this flag in conjunction with appropriate RewriteConds to conditionally block some URLs. - '
gone|G' (force URL to be gone)
This forces the current URL to be gone, i.e., it immediately sends back a HTTP response of 410 (GONE). Use this flag to mark pages which no longer exist as gone. - '
proxy|P' (force proxy)
This flag forces the substitution part to be internally forced as a proxy request and immediately (i.e., rewriting rule processing stops here) put through the proxy module. You have to make sure that the substitution string is a valid URI (e.g., typically starting with http://hostname) which can be handled by the Apache proxy module. If not you get an error from the proxy module. Use this flag to achieve a more powerful implementation of the ProxyPass directive, to map some remote stuff into the namespace of the local server. Notice: To use this functionality make sure you have the proxy module compiled into your Apache server program. If you don't know please check whether mod_proxy.c is part of the ``httpd -l'' output. If yes, this functionality is available to mod_rewrite. If not, then you first have to rebuild the ``httpd'' program with mod_proxy enabled. - '
last|L' (last rule)
Stop the rewriting process here and don't apply any more rewriting rules. This corresponds to the Perl last command or the break command from the C language. Use this flag to prevent the currently rewritten URL from being rewritten further by following rules. For example, use it to rewrite the root-path URL ('/') to a real one, e.g., '/e/www/'. - '
next|N' (next round)
Re-run the rewriting process (starting again with the first rewriting rule). Here the URL to match is again not the original URL but the URL from the last rewriting rule. This corresponds to the Perl next command or the continue command from the C language. Use this flag to restart the rewriting process, i.e., to immediately go to the top of the loop.
But be careful not to create an infinite loop! - '
chain|C' (chained with next rule)
This flag chains the current rule with the next rule (which itself can be chained with the following rule, etc.). This has the following effect: if a rule matches, then processing continues as usual, i.e., the flag has no effect. If the rule does not match, then all following chained rules are skipped. For instance, use it to remove the ``.www'' part inside a per-directory rule set when you let an external redirect happen (where the ``.www'' part should not to occur!). - '
type|T=MIME-type' (force MIME type)
Force the MIME-type of the target file to be MIME-type. For instance, this can be used to simulate the mod_alias directive ScriptAlias which internally forces all files inside the mapped directory to have a MIME type of ``application/x-httpd-cgi''. - '
nosubreq|NS' (used only if no internal sub-request)
This flag forces the rewriting engine to skip a rewriting rule if the current request is an internal sub-request. For instance, sub-requests occur internally in Apache when mod_include tries to find out information about possible directory default files (index.xxx). On sub-requests it is not always useful and even sometimes causes a failure to if the complete set of rules are applied. Use this flag to exclude some rules.
Use the following rule for your decision: whenever you prefix some URLs with CGI-scripts to force them to be processed by the CGI-script, the chance is high that you will run into problems (or even overhead) on sub-requests. In these cases, use this flag. - '
nocase|NC' (no case)
This makes the Pattern case-insensitive, i.e., there is no difference between 'A-Z' and 'a-z' when Pattern is matched against the current URL. - '
qsappend|QSA' (query string append)
This flag forces the rewriting engine to append a query string part in the substitution string to the existing one instead of replacing it. Use this when you want to add more data to the query string via a rewrite rule. - '
noescape|NE' (no URI escaping of output)
This flag keeps mod_rewrite from applying the usual URI escaping rules to the result of a rewrite. Ordinarily, special characters (such as '%', '$', ';', and so on) will be escaped into their hexcode equivalents ('%25', '%24', and '%3B', respectively); this flag prevents this from being done. This allows percent symbols to appear in the output, as in RewriteRule /foo/(.*) /bar?arg=P1\%3d$1 [R,NE] which would turn '/foo/zed' into a safe request for '/bar?arg=P1=zed'. Notice: The noescape flag is only available with Apache 1.3.20 and later versions. |
- '
passthrough|PT' (pass through to next handler)
This flag forces the rewriting engine to set the uri field of the internal request_rec structure to the value of the filename field. This flag is just a hack to be able to post-process the output of RewriteRule directives by Alias, ScriptAlias, Redirect, etc. directives from other URI-to-filename translators. A trivial example to show the semantics: If you want to rewrite /abc to /def via the rewriting engine of mod_rewrite and then /def to /ghi with mod_alias: RewriteRule ^/abc(.*) /def$1 [PT] Alias /def /ghi If you omit the PT flag then mod_rewrite will do its job fine, i.e., it rewrites uri=/abc/... to filename=/def/... as a full API-compliant URI-to-filename translator should do. Then mod_alias comes and tries to do a URI-to-filename transition which will not work. Note: You have to use this flag if you want to intermix directives of different modules which contain URL-to-filename translators. The typical example is the use of mod_alias and mod_rewrite.. - '
skip|S=num' (skip next rule(s))
This flag forces the rewriting engine to skip the next num rules in sequence when the current rule matches. Use this to make pseudo if-then-else constructs: The last rule of the then-clause becomes skip=N where N is the number of rules in the else-clause. (This is not the same as the 'chain|C' flag!) - '
env|E=VAR:VAL' (set environment variable)
This forces an environment variable named VAR to be set to the value VAL, where VAL can contain regexp backreferences $N and %N which will be expanded. You can use this flag more than once to set more than one variable. The variables can be later dereferenced in many situations, but usually from within XSSI (via <!--#echo var="VAR"-->) or CGI (e.g. $ENV{'VAR'}). Additionally you can dereference it in a following RewriteCond pattern via %{ENV:VAR}. Use this to strip but remember information from URLs.
| Note: Never forget that Pattern is applied to a complete URL in per-server configuration files. But in per-directory configuration files, the per-directory prefix (which always is the same for a specific directory!) is automatically removed for the pattern matching and automatically added after the substitution has been done. This feature is essential for many sorts of rewriting, because without this prefix stripping you have to match the parent directory which is not always possible. There is one exception: If a substitution string starts with ``http://'' then the directory prefix will not be added and an external redirect or proxy throughput (if flag P is used!) is forced! |
Note: To enable the rewriting engine for per-directory configuration files you need to set ``RewriteEngine On'' in these files and ``Options FollowSymLinks'' must be enabled. If your administrator has disabled override of FollowSymLinks for a user's directory, then you cannot use the rewriting engine. This restriction is needed for security reasons. |
Here are all possible substitution combinations and their meanings: Inside per-server configuration (httpd.conf)
for request ``GET /somepath/pathinfo'':
Given Rule Resulting Substitution---------------------------------------------- ----------------------------------^/somepath(.*) otherpath$1 not supported, because invalid!^/somepath(.*) otherpath$1 [R] not supported, because invalid!^/somepath(.*) otherpath$1 [P] not supported, because invalid!---------------------------------------------- ----------------------------------^/somepath(.*) /otherpath$1 /otherpath/pathinfo^/somepath(.*) /otherpath$1 [R] http://thishost/otherpath/pathinfo via external redirection^/somepath(.*) /otherpath$1 [P] not supported, because silly!---------------------------------------------- ----------------------------------^/somepath(.*) http://thishost/otherpath$1 /otherpath/pathinfo^/somepath(.*) http://thishost/otherpath$1 [R] http://thishost/otherpath/pathinfo via external redirection^/somepath(.*) http://thishost/otherpath$1 [P] not supported, because silly!---------------------------------------------- ----------------------------------^/somepath(.*) http://otherhost/otherpath$1 http://otherhost/otherpath/pathinfo via external redirection^/somepath(.*) http://otherhost/otherpath$1 [R] http://otherhost/otherpath/pathinfo via external redirection (the [R] flag is redundant)^/somepath(.*) http://otherhost/otherpath$1 [P] http://otherhost/otherpath/pathinfo via internal proxy |
Inside per-directory configuration for /somepath
(i.e., file .htaccess in dir /physical/path/to/somepath containing RewriteBase /somepath)
for request ``GET /somepath/localpath/pathinfo'':
Given Rule Resulting Substitution---------------------------------------------- ----------------------------------^localpath(.*) otherpath$1 /somepath/otherpath/pathinfo^localpath(.*) otherpath$1 [R] http://thishost/somepath/otherpath/pathinfo via external redirection^localpath(.*) otherpath$1 [P] not supported, because silly!---------------------------------------------- ----------------------------------^localpath(.*) /otherpath$1 /otherpath/pathinfo^localpath(.*) /otherpath$1 [R] http://thishost/otherpath/pathinfo via external redirection^localpath(.*) /otherpath$1 [P] not supported, because silly!---------------------------------------------- ----------------------------------^localpath(.*) http://thishost/otherpath$1 /otherpath/pathinfo^localpath(.*) http://thishost/otherpath$1 [R] http://thishost/otherpath/pathinfo via external redirection^localpath(.*) http://thishost/otherpath$1 [P] not supported, because silly!---------------------------------------------- ----------------------------------^localpath(.*) http://otherhost/otherpath$1 http://otherhost/otherpath/pathinfo via external redirection^localpath(.*) http://otherhost/otherpath$1 [R] http://otherhost/otherpath/pathinfo via external redirection (the [R] flag is redundant)^localpath(.*) http://otherhost/otherpath$1 [P] http://otherhost/otherpath/pathinfo via internal proxy |
Example: We want to rewrite URLs of the form / Language /~ Realname /.../ File
into /u/ Username /.../ File . Language
We take the rewrite mapfile from above and save it under /path/to/file/map.txt. Then we only have to add the following lines to the Apache server configuration file: RewriteLog /path/to/file/rewrite.logRewriteMap real-to-user txt:/path/to/file/map.txtRewriteRule ^/([^/]+)/~([^/]+)/(.*)$ /u/${real-to-user:$2|nobody}/$3.$1
This module keeps track of two additional (non-standard) CGI/SSI environment variables named SCRIPT_URL and SCRIPT_URI. These contain the logical Web-view to the current resource, while the standard CGI/SSI variables SCRIPT_NAME and SCRIPT_FILENAME contain the physical System-view. Notice: These variables hold the URI/URL as they were initially requested, i.e., before any rewriting. This is important because the rewriting process is primarily used to rewrite logical URLs to physical pathnames. Example: SCRIPT_NAME=/sw/lib/w3s/tree/global/u/rse/.www/index.htmlSCRIPT_FILENAME=/u/rse/.www/index.htmlSCRIPT_URL=/u/rse/SCRIPT_URI=http://en1.engelschall.com/u/rse/
We also have an URL Rewriting Guide available, which provides a collection of practical solutions for URL-based problems. There you can find real-life rulesets and additional information about mod_rewrite.
Apache HTTP Server Version 1.3 
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