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Documentation fixes do not harm anyone, so I feel free to commit this

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English cleanup to the mod_rewrite documentation although we're in code
freeze state. But we should now really kick out the 1.3.12 baby. We're
already behind the proposed dates...

Submitted by: G.W. Haywood <ged@jubileegroup.co.uk>
Reviewed by: Ralf S. Engelschall


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@84654 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Ralf S. Engelschall
2000-02-21 07:35:35 +00:00
parent 2a1ed8bb9f
commit 4cdb8a376e
1 changed files with 132 additions and 133 deletions
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docs/manual/mod/mod_rewrite.html
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@ -81,13 +81,13 @@ matching.
<P>
This module operates on the full URLs (including the path-info part) both in
per-server context (<CODE>httpd.conf</CODE>) and per-directory context
(<CODE>.htaccess</CODE>) and even can generate query-string parts on result.
(<CODE>.htaccess</CODE>) 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.
<P>
But all this functionality and flexibility has its drawback: complexity. So
don't expect to understand this module in its whole in just one day.
don't expect to understand this entire module in just one day.
<P>
This module was invented and originally written in April 1996<BR>
@ -152,46 +152,46 @@ 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 was read and before any authorization
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 (<CODE>.htaccess</CODE>) where read,
but before the content handler is activated.
and after the per-directory config files (<CODE>.htaccess</CODE>) have been
read, but before the content handler is activated.
<P>
So, after a request comes in and Apache has determined the corresponding
server (or virtual server) the rewriting engine start processing of all
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 either rewrites URLs to new
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 this way when the API
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:
<OL>
<LI>The API currently provides only a URL-to-filename hook. Although
mod_rewrite rewrites URLs to URLs, URLs to filenames and even
filenames to filenames. 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
then the API intends for it.
<LI>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.
<P>
<LI>Unbelievably mod_rewrite provides URL manipulations in per-directory
context, <EM>i.e.</EM>, within <CODE>.htaccess</CODE> files, although
these are
reached a very long time after the URLs were translated to filenames (this
has to be this way, because <CODE>.htaccess</CODE> files stay in the
filesystem, so processing has already been reached this stage of
processing). 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 it usually impossible, but see the
<CODE>RewriteBase</CODE> directive below for the trick to achieve this)
and then initiates a new internal sub-request with the new URL. This leads
to a new processing of the API phases from the beginning.
context, <EM>i.e.</EM>, within <CODE>.htaccess</CODE> files,
although these are reached a very long time after the URLs have
been translated to filenames. It has to be this way because
<CODE>.htaccess</CODE> 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 <CODE>RewriteBase</CODE>
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.
<P>
Again mod_rewrite tries hard to make this complicated step totally
transparent to the user, but you should remember here: While URL
@ -208,21 +208,21 @@ 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 while the directory walk of the
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. Just the final result processing is
same for both configuration contexts. Only the final result processing is
different.
<P>
The order of rules in the ruleset is important because the rewriting engine
processes them in a special order. And this order is not very obvious. The
processes them in a special (and not very obvious) order. The
rule is this: The rewriting engine loops through the ruleset rule by rule
(<CODE>RewriteRule</CODE> directives!) and when a particular rule matched it
(<CODE>RewriteRule</CODE> directives) and when a particular rule matches it
optionally loops through existing corresponding conditions
(<CODE>RewriteCond</CODE> directives). Because of historical reasons the
conditions are given first, the control flow is a little bit winded. See
(<CODE>RewriteCond</CODE> 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.
<P>
@ -245,29 +245,29 @@ Figure 1 for more details.
<P>
As you can see, first the URL is matched against the <EM>Pattern</EM> of each
rule. When it fails mod_rewrite immediately stops processing this rule and
continues with the next rule. If the <EM>Pattern</EM> matched, mod_rewrite
continues with the next rule. If the <EM>Pattern</EM> 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
<EM>Substitution</EM> and goes on with its rule-looping. But
if conditions exists, it starts an inner loop for processing them in order
they are listed. For conditions the logic is different: We don't match a
<EM>Substitution</EM> 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
<EM>TestString</EM> by expanding variables, back-references, map lookups,
<EM>etc.</EM> and then we try to match <EM>CondPattern</EM> 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 condition is available. If all conditions matched processing is
continued with the substitution of the URL with <EM>Substitution</EM>.
until no more conditions are available. If all conditions match, processing
is continued with the substitution of the URL with <EM>Substitution</EM>.
<H2><A NAME="InternalBackRefs">Regex Back-Reference Availability</A></H2>
One important thing here has to be remembered: Whenever you
use parenthesis in <EM>Pattern</EM> or in one of the <EM>CondPattern</EM>
back-reference are internally created which can be used with the
strings <CODE>$N</CODE> and <CODE>%N</CODE> (see below). And these
use parentheses in <EM>Pattern</EM> or in one of the <EM>CondPattern</EM>
back-references are internally created which can be used with the
strings <CODE>$N</CODE> and <CODE>%N</CODE> (see below). These
are available for creating the strings <EM>Substitution</EM> and
<EM>TestCond</EM>. Figure 2 shows at which locations the back-references are
transfered to for expansion.
<EM>TestCond</EM>. Figure 2 shows to which locations the back-references are
transfered for expansion.
<P>
<DIV ALIGN=CENTER>
@ -287,7 +287,7 @@ transfered to for expansion.
</DIV>
<P>
We know, this was a crash course of mod_rewrite's internal processing. But
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.
@ -342,12 +342,12 @@ environment variables.
<P>
Use this directive to disable the module instead of commenting out
all <CODE>RewriteRule</CODE> directives!
all the <CODE>RewriteRule</CODE> directives!
<P>
Note that, by default, rewrite configurations are not inherited.
This means that you need to have a <CODE>RewriteEngine on</CODE>
directive for each virtual host you wish to use it in.
directive for each virtual host in which you wish to use it.
<P>
<HR NOSHADE SIZE=1>
@ -393,9 +393,9 @@ strings can be one of the following:
<LI>'<STRONG><CODE>inherit</CODE></STRONG>'<BR>
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 gets inherited. In per-directory
conditions and rules of the main server are inherited. In per-directory
context this means that conditions and rules of the parent directory's
<CODE>.htaccess</CODE> configuration gets inherited.
<CODE>.htaccess</CODE> configuration are inherited.
</UL>
<P>
@ -442,10 +442,10 @@ config.
<P>
<TABLE WIDTH="70%" BORDER=0 BGCOLOR="#E0E0F0" CELLSPACING=0 CELLPADDING=10>
<TR><TD>
<STRONG>Notice</STRONG>: To disable the logging of rewriting actions it is
<STRONG>Note</STRONG>: To disable the logging of rewriting actions it is
not recommended to set <EM>Filename</EM>
to <CODE>/dev/null</CODE>, because although the rewriting engine does
not create output to a logfile it still creates the logfile
not then output to a logfile it still creates the logfile
output internally. <STRONG>This will slow down the server with no advantage
to the administrator!</STRONG>
To disable logging either remove or comment out the
@ -508,7 +508,7 @@ RewriteLog "/usr/local/var/apache/logs/rewrite.log"
><STRONG>Compatibility:</STRONG></A> Apache 1.2<BR>
<P>
The <CODE>RewriteLogLevel</CODE> directive set the verbosity level of the
The <CODE>RewriteLogLevel</CODE> 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.
@ -521,9 +521,8 @@ This disables all rewrite action logs.
<TABLE WIDTH="70%" BORDER=0 BGCOLOR="#E0E0F0" CELLSPACING=0 CELLPADDING=10>
<TR><TD>
<STRONG>Notice:</STRONG> Using a high value for <EM>Level</EM> will slow down
your Apache
server dramatically! Use the rewriting logfile only for debugging or at least
at <EM>Level</EM> not greater than 2!
your Apache server dramatically! Use the rewriting logfile at
a <EM>Level</EM> greater than 2 only for debugging!
</TD></TR>
</TABLE>
@ -575,7 +574,7 @@ This directive sets the filename for a synchronization lockfile which
mod_rewrite needs to communicate with <SAMP>RewriteMap</SAMP>
<EM>programs</EM>. 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
all other types of rewriting maps.
other types of rewriting maps.
<P>
<HR NOSHADE SIZE=1>
@ -634,7 +633,7 @@ When such a construct occurs the map <EM>MapName</EM>
is consulted and the key <EM>LookupKey</EM> is looked-up. If the key is
found, the map-function construct is substituted by <EM>SubstValue</EM>. If
the key is not found then it is substituted by <EM>DefaultValue</EM> or
the empty string if no <EM>DefaultValue</EM> was specified.
by the empty string if no <EM>DefaultValue</EM> was specified.
<P>
The following combinations for <EM>MapType</EM> and <EM>MapSource</EM>
@ -683,8 +682,8 @@ RewriteMap real-to-user txt:/path/to/file/map.txt
special
post-processing feature: After looking up a value it is parsed according
to contained ``<CODE>|</CODE>'' characters which have the meaning of
``or''. Or
in other words: they indicate a set of alternatives from which the actual
``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
@ -761,13 +760,13 @@ close(TXT)</PRE></TD></TR>
MapType: <CODE>prg</CODE>, MapSource: Unix filesystem path to valid
regular file
<P>
Here the source is a Unix program, not a map file. To create it you can use
the language of your choice, but the result has to be a run-able Unix
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 (<EM>i.e.</EM>, either object-code or a script with the
magic cookie trick '<CODE>#!/path/to/interpreter</CODE>' as the first
line).
magic cookie trick '<CODE>#!/path/to/interpreter</CODE>' as the
first line).
<P>
This program gets started once at startup of the Apache servers and then
This program is started once at startup of the Apache servers and then
communicates with the rewriting engine over its <CODE>stdin</CODE> and
<CODE>stdout</CODE> file-handles. For each map-function lookup it will
receive the key to lookup as a newline-terminated string on
@ -783,8 +782,7 @@ close(TXT)</PRE></TD></TR>
#!/usr/bin/perl
$| = 1;
while (&lt;STDIN&gt;) {
# ...here any transformations
# or lookups should occur...
# ...put here any transformations or lookups...
print $_;
}
</PRE></TD></TR>
@ -792,15 +790,15 @@ while (&lt;STDIN&gt;) {
<P>
But be very careful:<BR>
<OL>
<LI>``<EM>Keep the program simple, stupid</EM>'' (KISS), because
if this program hangs it will lead to a hang of the Apache server
<LI>``<EM>Keep it simple, stupid</EM>'' (KISS), because
if this program hangs it will hang the Apache server
when the rule occurs.
<LI>Avoid one common mistake: never do buffered I/O on <CODE>stdout</CODE>!
This will cause a deadloop! Hence the ``<CODE>$|=1</CODE>'' in the
above example...
<LI>Use the <SAMP>RewriteLock</SAMP> directive to define a lockfile
mod_rewrite can use to synchronize the communication to the program.
Per default no such synchronization takes place.
By default no such synchronization takes place.
</OL>
</UL>
@ -813,7 +811,7 @@ this map in per-directory context.
<P>
<TABLE WIDTH="70%" BORDER=0 BGCOLOR="#E0E0F0" CELLSPACING=0 CELLPADDING=10>
<TR><TD>
<STRONG>Notice:</STRONG> For plain text and DBM format files the looked-up
<STRONG>Note:</STRONG> For plain text and DBM format files the looked-up
keys are cached in-core
until the <CODE>mtime</CODE> of the mapfile changes or the server does a
restart. This way you can have map-functions in rules which are used
@ -863,15 +861,15 @@ per-directory rewrites. As you will see below, <CODE>RewriteRule</CODE> can be
used in per-directory config files (<CODE>.htaccess</CODE>). There it will act
locally, <EM>i.e.</EM>, 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.
it is automatically added back to the path.
<P>
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. <STRONG>But at most websites URLs are
<STRONG>NOT</STRONG> directly related to physical filename paths, so this
assumption will be usually be wrong!</STRONG> There you have to use the
NOT directly related to physical filename paths, so this
assumption will usually be wrong!</STRONG> There you have to use the
<CODE>RewriteBase</CODE> directive to specify the correct URL-prefix.
<P>
@ -902,7 +900,7 @@ directives.
RewriteEngine On
# let the server know that we are reached via /xyz and not
# let the server know that we were reached via /xyz and not
# via the physical path prefix /abc/def
RewriteBase /xyz
@ -920,7 +918,7 @@ rewritten to the physical file <CODE>/abc/def/newstuff.html</CODE>.
<TABLE WIDTH="70%" BORDER=0 BGCOLOR="#E0E0F0" CELLSPACING=0 CELLPADDING=10>
<TR><TD>
<FONT SIZE=-1>
<STRONG>Notice - For the Apache hackers:</STRONG><BR>
<STRONG>Note - For Apache hackers:</STRONG><BR>
The following list gives detailed information about the internal
processing steps:
@ -943,7 +941,7 @@ 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 internal to the Apache server and the same
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.
</FONT>
@ -1022,7 +1020,7 @@ the form
<CODE>%N</CODE>
</STRONG></BLOCKQUOTE>
(1 &lt;= N &lt;= 9) which provide access to the grouped parts (parenthesis!) of
(1 &lt;= N &lt;= 9) which provide access to the grouped parts (parentheses!) of
the pattern from the last matched <CODE>RewriteCond</CODE> directive in the
current bunch of conditions.
@ -1035,7 +1033,7 @@ current bunch of conditions.
</STRONG></BLOCKQUOTE>
where <EM>NAME_OF_VARIABLE</EM> can be a string
of the following list:
taken from the following list:
<P>
<TABLE BGCOLOR="#F0F0F0" CELLSPACING=0 CELLPADDING=5>
@ -1114,7 +1112,7 @@ IS_SUBREQ<BR>
<P>
<TABLE WIDTH="70%" BORDER=0 BGCOLOR="#E0E0F0" CELLSPACING=0 CELLPADDING=10>
<TR><TD>
<STRONG>Notice:</STRONG> These variables all correspond to the similar named
<STRONG>Notice:</STRONG> These variables all correspond to the similarly named
HTTP MIME-headers, C variables of the Apache server or <CODE>struct tm</CODE>
fields of the Unix system.
</TD></TR>
@ -1151,7 +1149,7 @@ is the value of the HTTP header ``<CODE>Proxy-Connection:</CODE>''.
<LI>There is the special format <CODE>%{LA-U:variable}</CODE> for look-aheads
which perform an internal (URL-based) sub-request to determine the final value
of <EM>variable</EM>. Use this when you want to use a variable for rewriting
which actually is set later in an API phase and thus is not available at the
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
<CODE>REMOTE_USER</CODE> variable from within the per-server context
(<CODE>httpd.conf</CODE> file) you have to use <CODE>%{LA-U:REMOTE_USER}</CODE>
@ -1163,16 +1161,16 @@ authorization phases come <EM>before</EM> this phase, you just can use
<CODE>%{REMOTE_USER}</CODE> there.
<P>
<LI>There is the special format: <CODE>%{LA-F:variable}</CODE> which perform an
<LI>There is the special format: <CODE>%{LA-F:variable}</CODE> which performs an
internal (filename-based) sub-request to determine the final value of
<EM>variable</EM>. This is the most of the time the same as LA-U above.
<EM>variable</EM>. Most of the time this is the same as LA-U above.
</OL>
<P>
<EM>CondPattern</EM> is the condition pattern, <EM>i.e.</EM>, a regular
expression
which gets applied to the current instance of the <EM>TestString</EM>,
<EM>i.e.</EM>, <EM>TestString</EM> gets evaluated and then matched against
which is applied to the current instance of the <EM>TestString</EM>,
<EM>i.e.</EM>, <EM>TestString</EM> is evaluated and then matched against
<EM>CondPattern</EM>.
<P>
@ -1180,7 +1178,7 @@ which gets applied to the current instance of the <EM>TestString</EM>,
<EM>Extended Regular Expression</EM> with some additions:
<OL>
<LI>You can precede the pattern string with a '<CODE>!</CODE>' character
<LI>You can prefix the pattern string with a '<CODE>!</CODE>' character
(exclamation mark) to specify a <STRONG>non</STRONG>-matching pattern.
<P>
@ -1189,23 +1187,23 @@ There are some special variants of <EM>CondPatterns</EM>. Instead of real
regular expression strings you can also use one of the following:
<P>
<UL>
<LI>'<STRONG>&lt;CondPattern</STRONG>' (is lexicographically lower)<BR>
<LI>'<STRONG>&lt;CondPattern</STRONG>' (is lexically lower)<BR>
Treats the <EM>CondPattern</EM> as a plain string and compares it
lexicographically to <EM>TestString</EM> and results in a true expression if
<EM>TestString</EM> is lexicographically lower than <EM>CondPattern</EM>.
lexically to <EM>TestString</EM>. True if
<EM>TestString</EM> is lexically lower than <EM>CondPattern</EM>.
<P>
<LI>'<STRONG>&gt;CondPattern</STRONG>' (is lexicographically greater)<BR>
<LI>'<STRONG>&gt;CondPattern</STRONG>' (is lexically greater)<BR>
Treats the <EM>CondPattern</EM> as a plain string and compares it
lexicographically to <EM>TestString</EM> and results in a true expression if
<EM>TestString</EM> is lexicographically greater than <EM>CondPattern</EM>.
lexically to <EM>TestString</EM>. True if
<EM>TestString</EM> is lexically greater than <EM>CondPattern</EM>.
<P>
<LI>'<STRONG>=CondPattern</STRONG>' (is lexicographically equal)<BR>
<LI>'<STRONG>=CondPattern</STRONG>' (is lexically equal)<BR>
Treats the <EM>CondPattern</EM> as a plain string and compares it
lexicographically to <EM>TestString</EM> and results in a true expression if
<EM>TestString</EM> is lexicographically equal to <EM>CondPattern</EM>, i.e the
lexically to <EM>TestString</EM>. True if
<EM>TestString</EM> is lexically equal to <EM>CondPattern</EM>, i.e the
two strings are exactly equal (character by character).
If <EM>CondPattern</EM> is just <SAMP>""</SAMP> (two quotation marks) this
compares <EM>TestString</EM> against the empty string.
compares <EM>TestString</EM> to the empty string.
<P>
<LI>'<STRONG>-d</STRONG>' (is <STRONG>d</STRONG>irectory)<BR>
Treats the <EM>TestString</EM> as a pathname and
@ -1240,7 +1238,7 @@ your server's performance!
<TABLE WIDTH="70%" BORDER=0 BGCOLOR="#E0E0F0" CELLSPACING=0 CELLPADDING=10>
<TR><TD>
<STRONG>Notice:</STRONG>
All of these tests can also be prefixed by a not ('!') character
All of these tests can also be prefixed by an exclamation mark ('!')
to negate their meaning.
</TD></TR>
</TABLE>
@ -1258,7 +1256,7 @@ is a comma-separated list of the following flags:
<UL>
<LI>'<STRONG><CODE>nocase|NC</CODE></STRONG>' (<STRONG>n</STRONG>o <STRONG>c</STRONG>ase)<BR>
This makes the condition test case-insensitive, <EM>i.e.</EM>, there is
This makes the test case-insensitive, <EM>i.e.</EM>, there is
no difference between 'A-Z' and 'a-z' both in the expanded
<EM>TestString</EM> and the <EM>CondPattern</EM>.
<P>
@ -1272,7 +1270,7 @@ RewriteCond %{REMOTE_HOST} ^host2.* [OR]
RewriteCond %{REMOTE_HOST} ^host3.*
RewriteRule ...some special stuff for any of these hosts...
</PRE></BLOCKQUOTE>
Without this flag you had to write down the cond/rule three times.
Without this flag you would have to write the cond/rule three times.
</UL>
<P>
@ -1341,12 +1339,13 @@ rewriting rule. The <STRONG>definition order</STRONG> of these rules is
run-time.
<P>
<A NAME="patterns"><EM>Pattern</EM></A> can be (for Apache 1.1.x a System
V8 and for Apache 1.2.x a POSIX) <A NAME="regexp">regular expression</A>
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 original requested
URL, because there could be any number of rules before which already matched
and made alterations to it.
<A NAME="patterns"><EM>Pattern</EM></A> can be (for Apache
1.1.x a System V8 and for Apache 1.2.x and later a POSIX) <A
NAME="regexp">regular expression</A> 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 no
longer existingany number of rules may already have matched and made
alterations to it.
<P>
Some hints about the syntax of regular expressions:
@ -1388,8 +1387,8 @@ Some hints about the syntax of regular expressions:
<P>
For more information about regular expressions either have a look at your
local regex(3) manpage or its <CODE>src/regex/regex.3</CODE> copy in the
Apache 1.3 distribution. When you are interested in more detailed and deeper
information about regular expressions and its variants (POSIX regex, Perl
Apache 1.3 distribution. If you are interested in more detailed
information about regular expressions and their variants (POSIX regex, Perl
regex, <EM>etc.</EM>) have a look at the following dedicated book on this topic:
<BLOCKQUOTE>
@ -1403,9 +1402,9 @@ ISBN 1-56592-257-3<BR>
<P>
Additionally in mod_rewrite the NOT character ('<CODE>!</CODE>') is a possible
pattern prefix. This gives you the ability to negate a pattern; to say, for
instance: ``<EM>if the current URL does <STRONG>NOT</STRONG> match to this
pattern</EM>''. This can be used for special cases where it is better to match
the negative pattern or as a last default rule.
instance: ``<EM>if the current URL does <STRONG>NOT</STRONG> match this
pattern</EM>''. This can be used for exceptional cases, where it is easier to
match the negative pattern, or as a last default rule.
<P>
<TABLE WIDTH="70%" BORDER=0 BGCOLOR="#E0E0F0" CELLSPACING=0 CELLPADDING=10>
@ -1442,8 +1441,8 @@ the above list.
As already mentioned above, all the rewriting rules are applied to the
<EM>Substitution</EM> (in the order of definition in the config file). The
URL is <STRONG>completely replaced</STRONG> by the <EM>Substitution</EM> and the
rewriting process goes on until there are no more rules (unless explicitly
terminated by a <CODE><STRONG>L</STRONG></CODE> flag - see below).
rewriting process goes on until there are no more rules unless explicitly
terminated by a <CODE><STRONG>L</STRONG></CODE> flag - see below.
<P>
There is a special substitution string named '<CODE>-</CODE>' which means:
@ -1462,7 +1461,7 @@ substitution string with just the question mark.
<P>
<TABLE WIDTH="70%" BORDER=0 BGCOLOR="#E0E0F0" CELLSPACING=0 CELLPADDING=10>
<TR><TD>
<STRONG>Notice</STRONG>: There is a special feature. When you prefix a substitution
<STRONG>Note</STRONG>: There is a special feature: When you prefix a substitution
field with <CODE>http://</CODE><EM>thishost</EM>[<EM>:thisport</EM>] then
<STRONG>mod_rewrite</STRONG> automatically strips it out. This auto-reduction on
implicit external redirect URLs is a useful and important feature when
@ -1502,14 +1501,14 @@ comma-separated list of the following flags:
one of the following symbolic names: <CODE>temp</CODE> (default), <CODE>permanent</CODE>,
<CODE>seeother</CODE>.
Use it for rules which should
canonicalize the URL and gives it back to the client, <EM>e.g.</EM>, translate
canonicalize the URL and give it back to the client, <EM>e.g.</EM>, translate
``<CODE>/~</CODE>'' into ``<CODE>/u/</CODE>'' or always append a slash to
<CODE>/u/</CODE><EM>user</EM>, etc.<BR>
<P>
<STRONG>Notice:</STRONG> When you use this flag, make sure that the
<STRONG>Note:</STRONG> 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 <CODE>http://thishost[:thisport]/</CODE>, but rewriting goes on.
URL with <CODE>http://thishost[:thisport]/</CODE>, 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.
<P>
@ -1520,8 +1519,8 @@ comma-separated list of the following flags:
<P>
<LI>'<STRONG><CODE>gone|G</CODE></STRONG>' (force URL to be <STRONG>g</STRONG>one)<BR>
This forces the current URL to be gone, <EM>i.e.</EM>, it immediately sends back a
HTTP response of 410 (GONE). Use this flag to mark no longer existing
pages as gone.
HTTP response of 410 (GONE). Use this flag to mark pages which no longer
exist as gone.
<P>
<LI>'<STRONG><CODE>proxy|P</CODE></STRONG>' (force <STRONG>p</STRONG>roxy)<BR>
This flag forces the substitution part to be internally forced as a proxy
@ -1546,7 +1545,7 @@ comma-separated list of the following flags:
don't apply any more rewriting rules. This corresponds to the Perl
<CODE>last</CODE> command or the <CODE>break</CODE> command from the C
language. Use this flag to prevent the currently rewritten URL from being
rewritten further by following rules which may be wrong. For
rewritten further by following rules. For
example, use it to rewrite the root-path URL ('<CODE>/</CODE>') to a real
one, <EM>e.g.</EM>, '<CODE>/e/www/</CODE>'.
<P>
@ -1557,11 +1556,11 @@ comma-separated list of the following flags:
<CODE>next</CODE> command or the <CODE>continue</CODE> command from the C
language. Use this flag to restart the rewriting process, <EM>i.e.</EM>, to
immediately go to the top of the loop. <BR>
<STRONG>But be careful not to create a deadloop!</STRONG>
<STRONG>But be careful not to create an infinite loop!</STRONG>
<P>
<LI>'<STRONG><CODE>chain|C</CODE></STRONG>' (<STRONG>c</STRONG>hained with next rule)<BR>
This flag chains the current rule with the next rule (which itself can
also be chained with its following rule, <EM>etc.</EM>). This has the following
be chained with the following rule, <EM>etc.</EM>). This has the following
effect: if a rule matches, then processing continues as usual, <EM>i.e.</EM>, the
flag has no effect. If the rule does <STRONG>not</STRONG> match, then all following
chained rules are skipped. For instance, use it to remove the
@ -1622,7 +1621,7 @@ comma-separated list of the following flags:
translator should do. Then <CODE>mod_alias</CODE> comes and tries to do a
URI-to-filename transition which will not work.
<P>
Notice: <STRONG>You have to use this flag if you want to intermix directives
Note: <STRONG>You have to use this flag if you want to intermix directives
of different modules which contain URL-to-filename translators</STRONG>. The
typical example is the use of <CODE>mod_alias</CODE> and
<CODE>mod_rewrite</CODE>..
@ -1630,12 +1629,12 @@ comma-separated list of the following flags:
<TABLE WIDTH="70%" BORDER=0 BGCOLOR="#E0E0F0" CELLSPACING=0 CELLPADDING=10>
<TR><TD>
<font size=-1>
<STRONG>Notice - For the Apache hackers:</STRONG><BR>
<STRONG>Note - For Apache hackers:</STRONG><BR>
If the current Apache API had a
filename-to-filename hook additionally to the URI-to-filename hook then
we wouldn't need this flag! But without such a hook this flag is the
only solution. The Apache Group has discussed this problem and will
add such hooks into Apache version 2.0.
add such a hook in Apache version 2.0.
</FONT>
</TD></TR>
</TABLE>
@ -1644,7 +1643,7 @@ comma-separated list of the following flags:
This flag forces the rewriting engine to skip the next <EM>num</EM> 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
a <CODE>skip=N</CODE> where N is the number of rules in the else-clause.
<CODE>skip=N</CODE> where N is the number of rules in the else-clause.
(This is <STRONG>not</STRONG> the same as the 'chain|C' flag!)
<P>
<LI>'<STRONG><CODE>env|E=</CODE></STRONG><EM>VAR</EM>:<EM>VAL</EM>' (set <STRONG>e</STRONG>nvironment variable)<BR>
@ -1652,9 +1651,9 @@ comma-separated list of the following flags:
value <EM>VAL</EM>, where <EM>VAL</EM> can contain regexp backreferences
<CODE>$N</CODE> and <CODE>%N</CODE> which will be expanded. You can use this flag
more than once to set more than one variable. The variables can be later
dereferenced at a lot of situations, but the usual location will be from
dereferenced in many situations, but usually from
within XSSI (via <CODE>&lt;!--#echo var="VAR"--&gt;</CODE>) or CGI (<EM>e.g.</EM>
<CODE>$ENV{'VAR'}</CODE>). But additionally you can also dereference it in a
<CODE>$ENV{'VAR'}</CODE>). Additionally you can dereference it in a
following RewriteCond pattern via <CODE>%{ENV:VAR}</CODE>. Use this to strip
but remember information from URLs.
</UL>
@ -1662,16 +1661,16 @@ comma-separated list of the following flags:
<P>
<TABLE WIDTH="70%" BORDER=0 BGCOLOR="#E0E0F0" CELLSPACING=0 CELLPADDING=10>
<TR><TD>
<STRONG>Notice:</STRONG> Never forget that <EM>Pattern</EM> gets applied to a complete URL
<STRONG>Note:</STRONG> Never forget that <EM>Pattern</EM> is applied to a complete URL
in per-server configuration files. <STRONG>But in per-directory configuration
files, the per-directory prefix (which always is the same for a specific
directory!) gets automatically <EM>removed</EM> for the pattern matching and
directory!) is automatically <EM>removed</EM> for the pattern matching and
automatically <EM>added</EM> after the substitution has been done.</STRONG> 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.
<P>
There is one exception: If a substitution string starts with
``<CODE>http://</CODE>'' then the directory prefix will be <STRONG>not</STRONG> added and a
``<CODE>http://</CODE>'' then the directory prefix will <STRONG>not</STRONG> be added and an
external redirect or proxy throughput (if flag <STRONG>P</STRONG> is used!) is forced!
</TD></TR>
</TABLE>
@ -1679,9 +1678,9 @@ external redirect or proxy throughput (if flag <STRONG>P</STRONG> is used!) is f
<P>
<TABLE WIDTH="70%" BORDER=0 BGCOLOR="#E0E0F0" CELLSPACING=0 CELLPADDING=10>
<TR><TD>
<STRONG>Notice:</STRONG> To enable the rewriting engine for per-directory configuration files
<STRONG>Note:</STRONG> To enable the rewriting engine for per-directory configuration files
you need to set ``<CODE>RewriteEngine On</CODE>'' in these files <STRONG>and</STRONG>
``<CODE>Option FollowSymLinks</CODE>'' enabled. If your administrator has
``<CODE>Option FollowSymLinks</CODE>'' must be enabled. If your administrator has
disabled override of <CODE>FollowSymLinks</CODE> for a user's directory, then
you cannot use the rewriting engine. This restriction is needed for
security reasons.
@ -1835,7 +1834,7 @@ variables <CODE>SCRIPT_NAME</CODE> and <CODE>SCRIPT_FILENAME</CODE> contain the
<P>
Notice: These variables hold the URI/URL <EM>as they were initially
requested</EM>, <EM>i.e.</EM>, in a state <EM>before</EM> any rewriting. This is
requested</EM>, <EM>i.e.</EM>, <EM>before</EM> any rewriting. This is
important because the rewriting process is primarily used to rewrite logical
URLs to physical pathnames.