1 <?xml version="1.0" encoding="UTF-8" ?>
2 <!DOCTYPE manualpage SYSTEM "./style/manualpage.dtd">
3 <?xml-stylesheet type="text/xsl" href="./style/manual.en.xsl"?>
4 <!-- $LastChangedRevision$ -->
7 Licensed to the Apache Software Foundation (ASF) under one or more
8 contributor license agreements. See the NOTICE file distributed with
9 this work for additional information regarding copyright ownership.
10 The ASF licenses this file to You under the Apache License, Version 2.0
11 (the "License"); you may not use this file except in compliance with
12 the License. You may obtain a copy of the License at
14 http://www.apache.org/licenses/LICENSE-2.0
16 Unless required by applicable law or agreed to in writing, software
17 distributed under the License is distributed on an "AS IS" BASIS,
18 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
19 See the License for the specific language governing permissions and
20 limitations under the License.
23 <manualpage metafile="expr.xml.meta">
25 <title>Expressions in Apache HTTP Server</title>
28 <p>Historically, there are several syntax variants for expressions used to express
29 a condition in the different modules of the Apache HTTP Server.
30 There is some ongoing effort to only use a single variant, called <em>ap_expr</em>,
31 for all configuration directives.
32 This document describes the <em>ap_expr</em> expression parser.
34 <p>The <em>ap_expr</em> expression is intended to replace most other
35 expression variants in HTTPD. For example, the deprecated
36 <directive module="mod_ssl">SSLRequire</directive> expressions can be
37 replaced by <a href="mod/mod_authz_core.html#reqexpr">Require expr</a>.
41 <seealso><directive module="core" type="section">If</directive></seealso>
42 <seealso><directive module="core" type="section">ElseIf</directive></seealso>
43 <seealso><directive module="core" type="section">Else</directive></seealso>
44 <seealso><directive module="mod_rewrite">RewriteCond</directive></seealso>
45 <seealso><directive module="mod_setenvif">SetEnvIfExpr</directive></seealso>
46 <seealso><directive module="mod_headers">Header</directive></seealso>
47 <seealso><directive module="mod_headers">RequestHeader</directive></seealso>
48 <seealso><directive module="mod_filter">FilterProvider</directive></seealso>
49 <seealso><a href="mod/mod_authz_core.html#reqexpr">Require expr</a></seealso>
50 <seealso><directive module="mod_ssl">SSLRequire</directive></seealso>
51 <seealso><directive module="mod_log_debug">LogMessage</directive></seealso>
52 <seealso><module>mod_include</module></seealso>
54 <section id="grammar">
55 <title>Grammar in Backus–Naur Form notation</title>
56 <p><a href="http://en.wikipedia.org/wiki/Backus%E2%80%93Naur_Form">Backus–Naur Form</a> (BNF) is a notation
57 technique for context-free grammars, often used to describe the syntax of languages used in computing.
61 expr ::= "<strong>true</strong>" | "<strong>false</strong>"
62 | "<strong>!</strong>" expr
63 | expr "<strong>&&</strong>" expr
64 | expr "<strong>||</strong>" expr
65 | "<strong>(</strong>" expr "<strong>)</strong>"
72 | word "<strong>in</strong>" "<strong>{</strong>" wordlist "<strong>}</strong>"
73 | word "<strong>in</strong>" listfunction
74 | word "<strong>=~</strong>" regex
75 | word "<strong>!~</strong>" regex
78 stringcomp ::= word "<strong>==</strong>" word
79 | word "<strong>!=</strong>" word
80 | word "<strong><</strong>" word
81 | word "<strong><=</strong>" word
82 | word "<strong>></strong>" word
83 | word "<strong>>=</strong>" word
85 integercomp ::= word "<strong>-eq</strong>" word | word "<strong>eq</strong>" word
86 | word "<strong>-ne</strong>" word | word "<strong>ne</strong>" word
87 | word "<strong>-lt</strong>" word | word "<strong>lt</strong>" word
88 | word "<strong>-le</strong>" word | word "<strong>le</strong>" word
89 | word "<strong>-gt</strong>" word | word "<strong>gt</strong>" word
90 | word "<strong>-ge</strong>" word | word "<strong>ge</strong>" word
93 | wordlist "<strong>,</strong>" word
95 word ::= word "<strong>.</strong>" word
97 | "<strong>'</strong>" string "<strong>'</strong>"
98 | "<strong>"</strong>" string "<strong>"</strong>"
103 string ::= stringpart
106 stringpart ::= cstring
113 variable ::= "<strong>%{</strong>" varname "<strong>}</strong>"
114 | "<strong>%{</strong>" funcname "<strong>:</strong>" funcargs "<strong>}</strong>"
116 rebackref ::= "<strong>$</strong>" [0-9]
118 function ::= funcname "<strong>(</strong>" word "<strong>)</strong>"
120 listfunction ::= listfuncname "<strong>(</strong>" word "<strong>)</strong>"
127 <title>Variables</title>
129 <p>The expression parser provides a number of variables of the form
130 <code>%{HTTP_HOST}</code>. Note that the value of a variable may depend
131 on the phase of the request processing in which it is evaluated. For
132 example, an expression used in an <directive><If ></directive>
133 directive is evaluated before authentication is done. Therefore,
134 <code>%{REMOTE_USER}</code> will not be set in this case.</p>
136 <p>The following variables provide the values of the named HTTP request
137 headers. The values of other headers can be obtained witht the
138 <code>req</code> <a href="#functions">function</a>.</p>
140 <table border="1" style="zebra">
141 <columnspec><column width="1"/></columnspec>
143 <tr><th>Name</th></tr>
144 <tr><td><code>HTTP_ACCEPT</code></td></tr>
145 <tr><td><code>HTTP_FORWARDED</code></td></tr>
146 <tr><td><code>HTTP_HOST</code></td></tr>
147 <tr><td><code>HTTP_PROXY_CONNECTION</code></td></tr>
148 <tr><td><code>HTTP_REFERER</code></td></tr>
149 <tr><td><code>HTTP_USER_AGENT</code></td></tr>
153 <p>Other request related variables</p>
155 <table border="1" style="zebra">
156 <columnspec><column width=".4"/><column width=".6"/></columnspec>
158 <tr><th>Name</th><th>Description</th></tr>
159 <tr><td><code>REQUEST_METHOD</code></td>
160 <td>The HTTP method of the incoming request (e.g.
161 <code>GET</code>)</td></tr>
162 <tr><td><code>REQUEST_SCHEME</code></td>
163 <td>The scheme part of the request's URI</td></tr>
164 <tr><td><code>REQUEST_URI</code></td>
165 <td>The path part of the request's URI</td></tr>
166 <tr><td><code>DOCUMENT_URI</code></td>
167 <td>Same as REQUEST_URI</td></tr>
168 <tr><td><code>REQUEST_FILENAME</code></td>
169 <td>The full local filesystem path to the file or script matching the
170 request, if this has already been determined by the server at the
171 time <code>REQUEST_FILENAME</code> is referenced. Otherwise, such
172 as when used in virtual host context, the same value as
173 <code>REQUEST_URI</code> </td></tr>
174 <tr><td><code>SCRIPT_FILENAME</code></td>
175 <td>Same as <code>REQUEST_FILENAME</code></td></tr>
176 <tr><td><code>LAST_MODIFIED</code></td>
177 <td>The date and time of last modification of the file in the format
178 <code>20101231235959</code>, if this has already been determined by
179 the server at the time <code>LAST_MODIFIED</code> is referenced.
181 <tr><td><code>SCRIPT_USER</code></td>
182 <td>The user name of the owner of the script.</td></tr>
183 <tr><td><code>SCRIPT_GROUP</code></td>
184 <td>The group name of the group of the script.</td></tr>
185 <tr><td><code>PATH_INFO</code></td>
186 <td>The trailing path name information, see
187 <directive module="core">AcceptPathInfo</directive></td></tr>
188 <tr><td><code>QUERY_STRING</code></td>
189 <td>The query string of the current request</td></tr>
190 <tr><td><code>IS_SUBREQ</code></td>
191 <td>"<code>true</code>" if the current request is a subrequest,
192 "<code>false</code>" otherwise</td></tr>
193 <tr><td><code>THE_REQUEST</code></td>
194 <td>The complete request line (e.g.,
195 "<code>GET /index.html HTTP/1.1</code>")</td></tr>
196 <tr><td><code>REMOTE_ADDR</code></td>
197 <td>The IP address of the remote host</td></tr>
198 <tr><td><code>REMOTE_HOST</code></td>
199 <td>The host name of the remote host</td></tr>
200 <tr><td><code>REMOTE_USER</code></td>
201 <td>The name of the authenticated user (if any)</td></tr>
202 <tr><td><code>REMOTE_IDENT</code></td>
203 <td>The user name set by <module>mod_ident</module></td></tr>
204 <tr><td><code>SERVER_NAME</code></td>
205 <td>The <directive module="core">ServerName</directive> of
206 the current vhost</td></tr>
207 <tr><td><code>SERVER_PORT</code></td>
208 <td>The server port of the current vhost, see
209 <directive module="core">ServerName</directive></td></tr>
210 <tr><td><code>SERVER_ADMIN</code></td>
211 <td>The <directive module="core">ServerAdmin</directive> of
212 the current vhost</td></tr>
213 <tr><td><code>SERVER_PROTOCOL</code></td>
214 <td>The protocol used by the request</td></tr>
215 <tr><td><code>DOCUMENT_ROOT</code></td>
216 <td>The <directive module="core">DocumentRoot</directive> of
217 the current vhost</td></tr>
218 <tr><td><code>AUTH_TYPE</code></td>
219 <td>The configured <directive module="mod_authn_core">AuthType</directive>
220 (e.g. "<code>basic</code>")</td></tr>
221 <tr><td><code>CONTENT_TYPE</code></td>
222 <td>The content type of the response</td></tr>
223 <tr><td><code>HANDLER</code></td>
224 <td>The name of the <a href="handler.html">handler</a> creating
225 the response</td></tr>
226 <tr><td><code>HTTPS</code></td>
227 <td>"<code>on</code>" if the request uses https,
228 "<code>off</code>" otherwise</td></tr>
229 <tr><td><code>IPV6</code></td>
230 <td>"<code>on</code>" if the connection uses IPv6,
231 "<code>off</code>" otherwise</td></tr>
232 <tr><td><code>REQUEST_STATUS</code></td>
233 <td>The HTTP error status of the request</td></tr>
234 <tr><td><code>REQUEST_LOG_ID</code></td>
235 <td>The error log id of the request (see
236 <directive module="core">ErrorLogFormat</directive>)</td></tr>
237 <tr><td><code>CONN_LOG_ID</code></td>
238 <td>The error log id of the connection (see
239 <directive module="core">ErrorLogFormat</directive>)</td></tr>
243 <p>Misc variables</p>
245 <table border="1" style="zebra">
246 <columnspec><column width=".4"/><column width=".6"/></columnspec>
248 <tr><th>Name</th><th>Description</th></tr>
249 <tr><td><code>TIME_YEAR</code></td>
250 <td>The current year (e.g. <code>2010</code>)</td></tr>
251 <tr><td><code>TIME_MON</code></td>
252 <td>The current month (<code>1</code>, ..., <code>12</code>)</td></tr>
253 <tr><td><code>TIME_DAY</code></td>
254 <td>The current day of the month</td></tr>
255 <tr><td><code>TIME_HOUR</code></td>
256 <td>The hour part of the current time
257 (<code>0</code>, ..., <code>23</code>)</td></tr>
258 <tr><td><code>TIME_MIN</code></td>
259 <td>The minute part of the current time </td></tr>
260 <tr><td><code>TIME_SEC</code></td>
261 <td>The second part of the current time </td></tr>
262 <tr><td><code>TIME_WDAY</code></td>
263 <td>The day of the week (starting with <code>0</code>
264 for Sunday)</td></tr>
265 <tr><td><code>TIME</code></td>
266 <td>The date and time in the format <code>20101231235959</code></td></tr>
267 <tr><td><code>SERVER_SOFTWARE</code></td>
268 <td>The server version string</td></tr>
269 <tr><td><code>API_VERSION</code></td>
270 <td>The date of the API version (module magic number)</td></tr>
273 <p>Some modules register additional variables, see e.g. <module>mod_ssl</module>.</p>
278 <title>Binary operators</title>
280 <p>With the exception of some built-in comparison operators, binary
281 operators have the form "<code>-[a-zA-Z][a-zA-Z0-9_]+</code>", i.e. a
282 minus and at least two characters. The name is not case sensitive.
283 Modules may register additional binary operators.</p>
286 <title>Comparison operators</title>
288 <table border="1" style="zebra">
289 <columnspec><column width=".2"/><column width=".2"/><column width=".6"/></columnspec>
291 <tr><th>Name</th><th>Alternative</th> <th>Description</th></tr>
292 <tr><td><code>==</code></td>
293 <td><code>=</code></td>
294 <td>String equality</td></tr>
295 <tr><td><code>!=</code></td>
297 <td>String inequality</td></tr>
298 <tr><td><code><</code></td>
300 <td>String less than</td></tr>
301 <tr><td><code><=</code></td>
303 <td>String less than or equal</td></tr>
304 <tr><td><code>></code></td>
306 <td>String greater than</td></tr>
307 <tr><td><code>>=</code></td>
309 <td>String greater than or equal</td></tr>
310 <tr><td><code>-eq</code></td>
311 <td><code>eq</code></td>
312 <td>Integer equality</td></tr>
313 <tr><td><code>-ne</code></td>
314 <td><code>ne</code></td>
315 <td>Integer inequality</td></tr>
316 <tr><td><code>-lt</code></td>
317 <td><code>lt</code></td>
318 <td>Integer less than</td></tr>
319 <tr><td><code>-le</code></td>
320 <td><code>le</code></td>
321 <td>Integer less than or equal</td></tr>
322 <tr><td><code>-gt</code></td>
323 <td><code>gt</code></td>
324 <td>Integer greater than</td></tr>
325 <tr><td><code>-ge</code></td>
326 <td><code>ge</code></td>
327 <td>Integer greater than or equal</td></tr>
331 <section id="binaryother">
332 <title>Other binary operators</title>
334 <table border="1" style="zebra">
335 <columnspec><column width=".2"/><column width=".8"/></columnspec>
337 <tr><th>Name</th><th>Description</th></tr>
338 <tr><td><code>-ipmatch</code></td>
339 <td>IP address matches address/netmask</td></tr>
340 <tr><td><code>-strmatch</code></td>
341 <td>left string matches pattern given by right string (containing
342 wildcards *, ?, [])</td></tr>
343 <tr><td><code>-strcmatch</code></td>
344 <td>same as <code>-strmatch</code>, but case insensitive</td></tr>
345 <tr><td><code>-fnmatch</code></td>
346 <td>same as <code>-strmatch</code>, but slashes are not matched by
354 <title>Unary operators</title>
356 <p>Unary operators take one argument and have the form
357 "<code>-[a-zA-Z]</code>", i.e. a minus and one character.
358 The name <em>is</em> case sensitive.
359 Modules may register additional unary operators.</p>
361 <table border="1" style="zebra">
362 <columnspec><column width=".2"/><column width=".2"/><column width=".6"/></columnspec>
364 <tr><th>Name</th><th>Description</th><th>Restricted</th></tr>
365 <tr><td><code>-d</code></td>
366 <td>The argument is treated as a filename.
367 True if the file exists and is a directory</td><td>yes</td></tr>
368 <tr><td><code>-e</code></td>
369 <td>The argument is treated as a filename.
370 True if the file (or dir or special) exists</td><td>yes</td></tr>
371 <tr><td><code>-f</code></td>
372 <td>The argument is treated as a filename.
373 True if the file exists and is regular file</td><td>yes</td></tr>
374 <tr><td><code>-L</code></td>
375 <td>The argument is treated as a filename.
376 True if the file exists and is symlink</td><td>yes</td></tr>
377 <tr><td><code>-h</code></td>
378 <td>The argument is treated as a filename.
379 True if the file exists and is symlink
380 (same as <code>-L</code>)</td><td>yes</td></tr>
381 <tr><td><code>-F</code></td>
382 <td>True if string is a valid file, accessible via all the server's
383 currently-configured access controls for that path. This uses an
384 internal subrequest to do the check, so use it with care - it can
385 impact your server's performance!</td><td></td></tr>
386 <tr><td><code>-U</code></td>
387 <td>True if string is a valid URL, accessible via all the server's
388 currently-configured access controls for that path. This uses an
389 internal subrequest to do the check, so use it with care - it can
390 impact your server's performance!</td><td></td></tr>
391 <tr><td><code>-A</code></td>
392 <td>Alias for <code>-U</code></td><td></td></tr>
393 <tr><td><code>-n</code></td>
394 <td>True if string is not empty</td><td></td></tr>
395 <tr><td><code>-z</code></td>
396 <td>True if string is empty</td><td></td></tr>
397 <tr><td><code>-T</code></td>
398 <td>False if string is empty, "<code>0</code>", "<code>off</code>",
399 "<code>false</code>", or "<code>no</code>" (case insensitive).
400 True otherwise.</td><td></td></tr>
401 <tr><td><code>-R</code></td>
402 <td>Same as "<code>%{REMOTE_ADDR} -ipmatch ...</code>", but more efficient
406 <p>The operators marked as "restricted" are not available in some modules
407 like <module>mod_include</module>.</p>
410 <section id="functions">
411 <title>Functions</title>
413 <p>Normal string-valued functions take one string as argument and return
414 a string. Functions names are not case sensitive.
415 Modules may register additional functions.</p>
417 <table border="1" style="zebra">
418 <columnspec><column width=".2"/><column width=".8"/></columnspec>
420 <tr><th>Name</th><th>Description</th><th>Restricted</th></tr>
421 <tr><td><code>req</code>, <code>http</code></td>
422 <td>Get HTTP request header</td><td></td></tr>
423 <tr><td><code>resp</code></td>
424 <td>Get HTTP response header</td><td></td></tr>
425 <tr><td><code>reqenv</code></td>
426 <td>Lookup request environment variable</td><td></td></tr>
427 <tr><td><code>osenv</code></td>
428 <td>Lookup operating system environment variable</td><td></td></tr>
429 <tr><td><code>note</code></td>
430 <td>Lookup request note</td><td></td></tr>
431 <tr><td><code>env</code></td>
432 <td>Return first match of <code>note</code>, <code>reqenv</code>,
433 <code>osenv</code></td><td></td></tr>
434 <tr><td><code>tolower</code></td>
435 <td>Convert string to lower case</td><td></td></tr>
436 <tr><td><code>toupper</code></td>
437 <td>Convert string to uppser case</td><td></td></tr>
438 <tr><td><code>escape</code></td>
439 <td>Escape special characters in %hex encoding</td><td></td></tr>
440 <tr><td><code>unescape</code></td>
441 <td>Unescape %hex encoded string, leaving encoded slashes alone;
442 return empty string if %00 is found</td><td></td></tr>
443 <tr><td><code>file</code></td>
444 <td>Read contents from a file</td><td>yes</td></tr>
445 <tr><td><code>filesize</code></td>
446 <td>Return size of a file (or 0 if file does not exist or is not
447 regular file)</td><td>yes</td></tr>
451 <p>The functions marked as "restricted" are not available in some modules
452 like <module>mod_include</module>.</p>
454 <p>In addition to string-valued functions, there are also list-valued functions which
455 take one string as argument and return a wordlist, i.e. a list of strings. The wordlist
456 can be used with the special <code>-in</code> operator.
457 Functions names are not case sensitive.
458 Modules may register additional functions.</p>
460 <p>There are no built-in list-valued functions. <module>mod_ssl</module>
461 provides <code>PeerExtList</code>. See the description of
462 <directive module="mod_ssl">SSLRequire</directive> for details
463 (but <code>PeerExtList</code> is also usable outside
464 of <directive module="mod_ssl">SSLRequire</directive>).</p>
471 <table border="1" style="zebra">
472 <columnspec><column width=".2"/><column width=".2"/><column width=".6"/></columnspec>
474 <tr><th>Name</th><th>Alternative</th> <th>Description</th></tr>
475 <tr><td><code>-in</code></td>
476 <td><code>in</code></td>
477 <td>string contained in string list</td></tr>
478 <tr><td><code>/regexp/</code></td>
479 <td><code>m#regexp#</code></td>
480 <td>Regular expression (the second form allows different delimiters than /)</td></tr>
481 <tr><td><code>/regexp/i</code></td>
482 <td><code>m#regexp#i</code></td>
483 <td>Case insensitive regular expression</td></tr>
484 <tr><td><code>$0 ... $9</code></td>
486 <td>Regular expression backreferences</td></tr>
489 <section id="rebackref">
490 <title>Regular expression backreferences</title>
491 <p>The strings <code>$0</code> ... <code>$9</code> allow to reference
492 the capture groups from a previously executed, successfully
493 matching regular expressions. They can normally only be used in the
494 same expression as the matching regex, but some modules allow special
500 <section id="sslrequire">
501 <title>Comparison with SSLRequire</title>
502 <p>The <em>ap_expr</em> syntax is mostly a superset of the syntax of the
503 deprecated <directive module="mod_ssl">SSLRequire</directive> directive.
504 The differences are described in <directive
505 module="mod_ssl">SSLRequire</directive>'s documentation.</p>