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Apache模块 mod_rewrite
| 说明 | 一个基于一定规则的实时重写URL请求的引擎 |
|---|---|
| 状态 | 扩展(E) |
| 模块名 | rewrite_module |
| 源文件 | mod_rewrite.c |
| 兼容性 | 仅在 Apache 1.3 及以后的版本中可用 |
概述
此模块提供了一个基于正则表达式分析器的重写引擎来实时重写URL请求。它支持每个完整规则可以拥有不限数量的子规则以及附加条件规则的灵活而且强大的URL操作机制。此URL操作可以依赖于各种测试，比如服务器变量、环境变量、HTTP头、时间标记，甚至各种格式的用于匹配URL组成部分的查找数据库。
此模块可以操作URL的所有部分(包括路径信息部分)，在服务器级的(httpd.conf)和目录级的(.htaccess)配置都有效，还可以生成最终请求字符串。此重写操作的结果可以是内部子处理，也可以是外部请求的转向，甚至还可以是内部代理处理。
但是，所有这些功能和灵活性带来一个问题，那就是复杂性，因此，不要指望一天之内就能看懂整个模块。
更多的讨论、细节、示例，请查看详细的URL重写文档。
特殊字符的引用
在Apache 1.3.20中，TestString和Substitution中的特殊字符可以用前导斜杠(\)来实现转义(即忽略其特殊含义而视之为普通字符)。 比如，Substitution可以用"\$"来包含一个美元符号，以避免mod_rewrite把它视为反向引用。
环境变量
此模块会跟踪两个额外的(非标准)CGI/SSI环境变量，SCRIPT_URL和SCRIPT_URI。他们包含了当前资源的逻辑网络视图，而标准CGI/SSI变量SCRIPT_NAME和SCRIPT_FILENAME包含的是物理系统视图。
注意：这些变量保持的是其最初被请求时的URI/URL，即在任何重写操作之前的URI/URL。其重要性在于他们是重写操作重写URL到物理路径名的原始依据。
示例
SCRIPT_NAME=/sw/lib/w3s/tree/global/u/rse/.www/index.html SCRIPT_FILENAME=/u/rse/.www/index.html SCRIPT_URL=/u/rse/ SCRIPT_URI=http://en1.engelschall.com/u/rse/
实用方案
我们提供了URL重写指南和高级URL重写指南文档，列举了许多基于URL的问题的实用方案，其中你可以找到真实有用的规则集。
RewriteBase 指令
| 说明 | 设置目录级重写的基准URL |
|---|---|
| 语法 | RewriteBase URL-path |
| 默认值 | 参见使用方法 |
| 作用域 | directory, .htaccess |
| 覆盖项 | FileInfo |
| 状态 | 扩展(E) |
| 模块 | mod_rewrite |
RewriteBase指令显式地设置了目录级重写的基准URL。在下文中，你可以看见RewriteRule可以用于目录级的配置文件中(.htaccess)并在局部范围内起作用，即规则实际处理的只是剥离了本地路径前缀的一部分。处理结束后，这个路径会被自动地附着回去。默认值是"RewriteBase physical-directory-path"。
在对一个新的URL进行替换时，此模块必须把这个URL重新注入到服务器处理中。为此，它必须知道其对应的URL前缀或者说URL基准。通常，此前缀就是对应的文件路径。但是，大多数网站URL不是直接对应于其物理文件路径的，因而一般不能做这样的假定! 所以在这种情况下，就必须用RewriteBase指令来指定正确的URL前缀。
RewriteBase指令，则必须在每个对应的.htaccess文件中指定RewriteRule 。例如，目录级配置文件内容如下：
# # /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 例如， # 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
上述例子中，对/xyz/oldstuff.html的请求被正确地重写为物理的文件/abc/def/newstuff.html 。
For Apache Hackers
以下列出了内部处理的详细步骤：
Request: /xyz/oldstuff.html Internal 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
虽然这个过程看来很繁复，但是由于目录级重写的到来时机已经太晚了，它不得不把这个(重写)请求重新注入到Apache核心中，所以Apache内部确实是这样处理的。但是：它的开销并不象看起来的那样大，因为重新注入完全在Apache服务器内部进行，而且这样的过程在Apache内部也为其他许多操作所使用。所以，你可以充分信任其设计和实现是正确的。
RewriteCond 指令
| 说明 | 定义重写发生的条件 |
|---|---|
| 语法 | RewriteCond TestString CondPattern |
| 作用域 | server config, virtual host, directory, .htaccess |
| 覆盖项 | FileInfo |
| 状态 | 扩展(E) |
| 模块 | mod_rewrite |
RewriteCond指令定义了一个规则的条件，即在一个RewriteRule指令之前有一个或多个RewriteCond指令。条件之后的重写规则仅在当前URI与pattern匹配并且符合这些条件的时候才会起作用。
TestString是一个纯文本的字符串，但是还可以包含下列可扩展的成分：
-
RewriteRule反向引用 ，引用方法是：
(0 <= N <= 9)引用当前(带有若干$NRewriteRule指令的)RewriteCond中的与pattern匹配的分组成分(圆括号!)。 -
RewriteCond反向引用 ，引用方法是：
(1 <= N <= 9)引用当前若干%NRewriteCond条件中最后符合的条件中的分组成分(圆括号!)。 -
RewriteMap扩展 ，引用方法是：
细节请参见RewriteMap 指令。${mapname:key|default} -
服务器变量 ，引用方法是：
NAME_OF_VARIABLE可以是下表列出的字符串之一：%{NAME_OF_VARIABLE}HTTP headers: connection & request: HTTP_USER_AGENT
HTTP_REFERER
HTTP_COOKIE
HTTP_FORWARDED
HTTP_HOST
HTTP_PROXY_CONNECTION
HTTP_ACCEPT
REMOTE_ADDR
REMOTE_HOST
REMOTE_PORT
REMOTE_USER
REMOTE_IDENT
REQUEST_METHOD
SCRIPT_FILENAME
PATH_INFO
QUERY_STRING
AUTH_TYPE
server internals: date and time: specials: DOCUMENT_ROOT
SERVER_ADMIN
SERVER_NAME
SERVER_ADDR
SERVER_PORT
SERVER_PROTOCOL
SERVER_SOFTWARE
TIME_YEAR
TIME_MON
TIME_DAY
TIME_HOUR
TIME_MIN
TIME_SEC
TIME_WDAY
TIME
API_VERSION
THE_REQUEST
REQUEST_URI
REQUEST_FILENAME
IS_SUBREQ
HTTPS
These variables all correspond to the similarly named HTTP MIME-headers, C variables of the Apache server or
struct tmfields 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.
HTTPS- Will contain the text "on" if the connection is
using SSL/TLS, or "off" otherwise. (This variable
can be safely used regardless of whether
mod_sslis loaded).
Special Notes:
- The variables SCRIPT_FILENAME and REQUEST_FILENAME
contain the same value, i.e., the value of the
filenamefield of the internalrequest_recstructure 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 theurifield ofrequest_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) viagetenv()from the Apache server process. - There is the special format:
%{SSL:variable}where variable is the name of an SSL environment variable; this can be used whether or notmod_sslis loaded, but will always expand to the empty string if it is not. Example:%{SSL:SSL_CIPHER_USEKEYSIZE}may expand to128. - 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 theREMOTE_USERvariable from within the per-server context (httpd.conffile) 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 (.htaccessfile) 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 perl compatible 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. - '-x' (has executable
permissions)
Treats the TestString as a pathname and tests if it exists and has execution permissions. These permissions are determined depending on the underlying OS. - '-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. - '<CondPattern' (is lexically
lower)
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和CondPattern. It has no effect on filesystem and subrequest checks. -
'
ornext|OR' (或 next condition)
Use this to combine rule conditions with a local OR instead of the implicit AND. Typical example:Without this flag you would have to write the cond/rule three times.RewriteCond %{REMOTE_HOST} ^host1.* [OR] RewriteCond %{REMOTE_HOST} ^host2.* [OR] RewriteCond %{REMOTE_HOST} ^host3.* RewriteRule ...some special stuff for any of these hosts...
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.
RewriteEngine 指令
| 说明 | Enables or disables runtime rewriting engine |
|---|---|
| 语法 | RewriteEngine on|off |
| 默认值 | RewriteEngine off |
| 作用域 | server config, virtual host, directory, .htaccess |
| 覆盖项 | FileInfo |
| 状态 | 扩展(E) |
| 模块 | mod_rewrite |
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.
RewriteLock 指令
| 说明 | Sets the name of the lock file used for RewriteMap
synchronization |
|---|---|
| 语法 | RewriteLock file-path |
| 作用域 | server config |
| 状态 | 扩展(E) |
| 模块 | mod_rewrite |
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.
RewriteLog 指令
| 说明 | Sets the name of the file used for logging rewrite engine processing |
|---|---|
| 语法 | RewriteLog file-path |
| 作用域 | server config, virtual host |
| 状态 | 扩展(E) |
| 模块 | mod_rewrite |
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.
/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!
安全
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.示例
RewriteLog "/usr/local/var/apache/logs/rewrite.log"
RewriteLogLevel 指令
| 说明 | Sets the verbosity of the log file used by the rewrite engine |
|---|---|
| 语法 | RewriteLogLevel Level |
| 默认值 | RewriteLogLevel 0 |
| 作用域 | server config, virtual host |
| 状态 | 扩展(E) |
| 模块 | mod_rewrite |
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.
示例
RewriteLogLevel 3
RewriteMap 指令
| 说明 | Defines a mapping function for key-lookup |
|---|---|
| 语法 | RewriteMap MapName MapType:MapSource
|
| 作用域 | server config, virtual host |
| 状态 | 扩展(E) |
| 模块 | mod_rewrite |
| 兼容性 | The choice of different dbm types is available in Apache 2.0.41 及以后的版本中可用 |
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.
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.
For example, you might define a
RewriteMap as:
RewriteMap examplemap txt:/path/to/file/map.txt
You would then be able to use this map in a
RewriteRule as follows:
RewriteRule ^/ex/(.*) ${examplemap:$1}
The following combinations for MapType和MapSource can be used:
-
Standard Plain Text
MapType:txt, MapSource: Unix filesystem path to valid regular fileThis is the standard rewriting map feature where the MapSource is a plain ASCII file containing either blank lines, comment lines (starting with a '#' character) or pairs like the following - one per line.
MatchingKey SubstValue
示例
## ## map.txt -- rewriting map ## Ralf.S.Engelschall rse # Bastard Operator From Hell Mr.Joe.Average joe # Mr. Average
RewriteMap real-to-user txt:/path/to/file/map.txt -
Randomized Plain Text
MapType:rnd, MapSource: Unix filesystem path to valid regular fileThis is identical to the Standard Plain Text variant above but with a special post-processing feature: After looking up a value it is parsed according to contained "
|" characters which have the meaning of "or". In other words they indicate a set of alternatives from which the actual returned value is chosen randomly. For example, you might use the following map file and directives to provide a random load balancing between several back-end server, via a reverse-proxy. Images are sent to one of the servers in the 'static' pool, while everything else is sent to one of the 'dynamic' pool.Example:
Rewrite map file
## ## map.txt -- rewriting map ## static www1|www2|www3|www4 dynamic www5|www6
Configuration directives
RewriteMap servers rnd:/path/to/file/map.txt
RewriteRule ^/(.*\.(png|gif|jpg)) http://${servers:static}/$1 [NC,P,L]
RewriteRule ^/(.*) http://${servers:dynamic}/$1 [P,L] -
Hash File
MapType:dbm[=type], MapSource: Unix filesystem path to valid regular fileHere the source is a binary format DBM file containing the same contents as a Plain Text format file, but in a special representation which is optimized for really fast lookups. The type can be sdbm, gdbm, ndbm, or db depending on compile-time settings. If the type is omitted, the compile-time default will be chosen. You can create such a file with any DBM tool or with the following Perl script. Be sure to adjust it to create the appropriate type of DBM. The example creates an NDBM file.
#!/path/to/bin/perl ## ## txt2dbm -- convert txt map to dbm format ## use NDBM_File; use Fcntl; ($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} = $2 if (/^\s*(\S+)\s+(\S+)/); } untie %DB; close(TXT);$ txt2dbm map.txt map.db -
Internal Function
MapType:int, MapSource: Internal Apache functionHere 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.
-
toupper:
-
External Rewriting Program
MapType:prg, MapSource: Unix filesystem path to valid regular fileHere 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和stdoutfile-handles. For each map-function lookup it will receive the key to lookup as a newline-terminated string onstdin. It then has to give back the looked-up value as a newline-terminated string onstdoutor 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
RewriteLockdirective to define a lockfile mod_rewrite can use to synchronize the communication to the program. By default no such synchronization takes place.
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.
注意
For plain text and DBM format files the looked-up keys are cached in-core until themtime 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!
RewriteOptions 指令
| 说明 | Sets some special options for the rewrite engine |
|---|---|
| 语法 | RewriteOptions Options |
| 作用域 | server config, virtual host, directory, .htaccess |
| 覆盖项 | FileInfo |
| 状态 | 扩展(E) |
| 模块 | mod_rewrite |
| 兼容性 |
MaxRedirects is no longer available in version 2.1 及以后的版本中可用 |
RewriteOptions directive sets some
special options for the current per-server or per-directory
configuration. The Option string can be currently only one:
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
.htaccessconfiguration are inherited.
RewriteRule 指令
| 说明 | Defines rules for the rewriting engine |
|---|---|
| 语法 | RewriteRule
Pattern Substitution |
| 作用域 | server config, virtual host, directory, .htaccess |
| 覆盖项 | FileInfo |
| 状态 | 扩展(E) |
| 模块 | mod_rewrite |
| 兼容性 | The cookie-flag is available in Apache 2.0.40 及以后的版本中可用 |
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 is a perl compatible 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 text2 Quantifiers:?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 anchor Escaping:\char escape that particular char (for instance to specify the chars ".[]()" etc.)
For more information about regular expressions have a look at the perl regular expression manpage ("perldoc perlre"). If you are interested in more detailed information about regular expressions and their variants (POSIX regex etc.) have a look at the following dedicated book on this topic:
Mastering Regular Expressions, 2nd Edition
Jeffrey E.F. Friedl
O'Reilly & Associates, Inc. 2002
ISBN 0-596-00289-0
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
$Nto the RewriteRule pattern - back-references
%Nto 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, 例如，in
conjunction with the C (chain) flag to be
able to have more than one pattern to be applied before a
substitution occurs.
Query String
Pattern will not match against the query string.
Instead, you must use a RewriteCond with the
%{QUERY_STRING} variable. You can, however, 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. To
combine a new query string with an old one, use the
[QSA] flag (see below).
Substitution of Absolute URLs
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:
- '
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!). -
'
cookie|CO=NAME:VAL:domain[:lifetime[:path]]' (set cookie)
This sets a cookie on the client's browser. The cookie's name is specified by NAME and the value is VAL. The domain field is the domain of the cookie, such as '.apache.org',the optional lifetime is the lifetime of the cookie in minutes, and the optional path is the path of the cookie -
'
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和%Nwhich 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 (例如，$ENV{'VAR'}). Additionally you can dereference it in a following RewriteCond pattern via%{ENV:VAR}. Use this to strip but remember information from URLs. - '
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. -
'
handler|H=Content-handler' (force Content handler)
Force the Content-handler of the target file to be Content-handler. For instance, this can be used to simulate themod_aliasdirectiveScriptAliaswhich internally forces all files inside the mapped directory to have a handler of "cgi-script". - '
last|L' (last rule)
Stop the rewriting process here and don't apply any more rewriting rules. This corresponds to the Perllastcommand or thebreakcommand 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, 例如，'/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 Perlnextcommand or thecontinuecommand 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! - '
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. -
'
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 inwhich would turn 'RewriteRule /foo/(.*) /bar?arg=P1\%3d$1 [R,NE]/foo/zed' into a safe request for '/bar?arg=P1=zed'. -
'
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 whenmod_includetries 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.
-
'
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 (例如，typically starting withhttp://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.注意：
mod_proxymust be enabled in order to use this flag. -
'
passthrough|PT' (pass through to next handler)
This flag forces the rewriting engine to set theurifield of the internalrequest_recstructure to the value of thefilenamefield. This flag is just a hack to be able to post-process the output ofRewriteRuledirectives byAlias,ScriptAlias,Redirect, etc. directives from other URI-to-filename translators. A trivial example to show the semantics: If you want to rewrite/abcto/defvia the rewriting engine ofmod_rewriteand then/defto/ghiwithmod_alias:If you omit theRewriteRule ^/abc(.*) /def$1 [PT]
Alias /def /ghiPTflag thenmod_rewritewill do its job fine, i.e., it rewritesuri=/abc/...tofilename=/def/...as a full API-compliant URI-to-filename translator should do. Thenmod_aliascomes 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和mod_rewrite.. - '
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. - '
redirect|R[=code]' (force redirect)
Prefix Substitution withhttp://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, 例如，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. - '
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 becomesskip=Nwhere N is the number of rules in the else-clause. (This is not the same as the 'chain|C' flag!) -
'
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 setup the content-type based on some conditions. For example, the following snippet allows.phpfiles to be displayed bymod_phpif they are called with the.phpsextension:RewriteRule ^(.+\.php)s$ $1 [T=application/x-httpd-php-source]
注意
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!
注意
To enable the rewriting engine for per-directory configuration files you need to set "RewriteEngine On" in these files
和 "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$1 [P] http://otherhost/otherpath/pathinfo
via internal proxy
Example:
We want to rewrite URLs of the form
/ Language /~
Realname /.../ File
into
/u/ Username /.../
File . Language
We take the rewrite mapfile from above and save it under
/path/to/file/map.txt. Then we only have to
add the following lines to the Apache server configuration
file:
RewriteLog /path/to/file/rewrite.log
RewriteMap real-to-user txt:/path/to/file/map.txt
RewriteRule ^/([^/]+)/~([^/]+)/(.*)$ /u/${real-to-user:$2|nobody}/$3.$1