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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>
240 <tr><td><code>CONN_REMOTE_ADDR</code></td>
241 <td>The peer IP address of the connection (see the
242 <module>mod_remoteip</module> module)</td></tr>
246 <p>Misc variables</p>
248 <table border="1" style="zebra">
249 <columnspec><column width=".4"/><column width=".6"/></columnspec>
251 <tr><th>Name</th><th>Description</th></tr>
252 <tr><td><code>TIME_YEAR</code></td>
253 <td>The current year (e.g. <code>2010</code>)</td></tr>
254 <tr><td><code>TIME_MON</code></td>
255 <td>The current month (<code>1</code>, ..., <code>12</code>)</td></tr>
256 <tr><td><code>TIME_DAY</code></td>
257 <td>The current day of the month</td></tr>
258 <tr><td><code>TIME_HOUR</code></td>
259 <td>The hour part of the current time
260 (<code>0</code>, ..., <code>23</code>)</td></tr>
261 <tr><td><code>TIME_MIN</code></td>
262 <td>The minute part of the current time </td></tr>
263 <tr><td><code>TIME_SEC</code></td>
264 <td>The second part of the current time </td></tr>
265 <tr><td><code>TIME_WDAY</code></td>
266 <td>The day of the week (starting with <code>0</code>
267 for Sunday)</td></tr>
268 <tr><td><code>TIME</code></td>
269 <td>The date and time in the format <code>20101231235959</code></td></tr>
270 <tr><td><code>SERVER_SOFTWARE</code></td>
271 <td>The server version string</td></tr>
272 <tr><td><code>API_VERSION</code></td>
273 <td>The date of the API version (module magic number)</td></tr>
276 <p>Some modules register additional variables, see e.g. <module>mod_ssl</module>.</p>
281 <title>Binary operators</title>
283 <p>With the exception of some built-in comparison operators, binary
284 operators have the form "<code>-[a-zA-Z][a-zA-Z0-9_]+</code>", i.e. a
285 minus and at least two characters. The name is not case sensitive.
286 Modules may register additional binary operators.</p>
289 <title>Comparison operators</title>
291 <table border="1" style="zebra">
292 <columnspec><column width=".2"/><column width=".2"/><column width=".6"/></columnspec>
294 <tr><th>Name</th><th>Alternative</th> <th>Description</th></tr>
295 <tr><td><code>==</code></td>
296 <td><code>=</code></td>
297 <td>String equality</td></tr>
298 <tr><td><code>!=</code></td>
300 <td>String inequality</td></tr>
301 <tr><td><code><</code></td>
303 <td>String less than</td></tr>
304 <tr><td><code><=</code></td>
306 <td>String less than or equal</td></tr>
307 <tr><td><code>></code></td>
309 <td>String greater than</td></tr>
310 <tr><td><code>>=</code></td>
312 <td>String greater than or equal</td></tr>
313 <tr><td><code>-eq</code></td>
314 <td><code>eq</code></td>
315 <td>Integer equality</td></tr>
316 <tr><td><code>-ne</code></td>
317 <td><code>ne</code></td>
318 <td>Integer inequality</td></tr>
319 <tr><td><code>-lt</code></td>
320 <td><code>lt</code></td>
321 <td>Integer less than</td></tr>
322 <tr><td><code>-le</code></td>
323 <td><code>le</code></td>
324 <td>Integer less than or equal</td></tr>
325 <tr><td><code>-gt</code></td>
326 <td><code>gt</code></td>
327 <td>Integer greater than</td></tr>
328 <tr><td><code>-ge</code></td>
329 <td><code>ge</code></td>
330 <td>Integer greater than or equal</td></tr>
334 <section id="binaryother">
335 <title>Other binary operators</title>
337 <table border="1" style="zebra">
338 <columnspec><column width=".2"/><column width=".8"/></columnspec>
340 <tr><th>Name</th><th>Description</th></tr>
341 <tr><td><code>-ipmatch</code></td>
342 <td>IP address matches address/netmask</td></tr>
343 <tr><td><code>-strmatch</code></td>
344 <td>left string matches pattern given by right string (containing
345 wildcards *, ?, [])</td></tr>
346 <tr><td><code>-strcmatch</code></td>
347 <td>same as <code>-strmatch</code>, but case insensitive</td></tr>
348 <tr><td><code>-fnmatch</code></td>
349 <td>same as <code>-strmatch</code>, but slashes are not matched by
357 <title>Unary operators</title>
359 <p>Unary operators take one argument and have the form
360 "<code>-[a-zA-Z]</code>", i.e. a minus and one character.
361 The name <em>is</em> case sensitive.
362 Modules may register additional unary operators.</p>
364 <table border="1" style="zebra">
365 <columnspec><column width=".2"/><column width=".2"/><column width=".6"/></columnspec>
367 <tr><th>Name</th><th>Description</th><th>Restricted</th></tr>
368 <tr><td><code>-d</code></td>
369 <td>The argument is treated as a filename.
370 True if the file exists and is a directory</td><td>yes</td></tr>
371 <tr><td><code>-e</code></td>
372 <td>The argument is treated as a filename.
373 True if the file (or dir or special) exists</td><td>yes</td></tr>
374 <tr><td><code>-f</code></td>
375 <td>The argument is treated as a filename.
376 True if the file exists and is regular file</td><td>yes</td></tr>
377 <tr><td><code>-s</code></td>
378 <td>The argument is treated as a filename.
379 True if the file exists and is not empty</td><td>yes</td></tr>
380 <tr><td><code>-L</code></td>
381 <td>The argument is treated as a filename.
382 True if the file exists and is symlink</td><td>yes</td></tr>
383 <tr><td><code>-h</code></td>
384 <td>The argument is treated as a filename.
385 True if the file exists and is symlink
386 (same as <code>-L</code>)</td><td>yes</td></tr>
387 <tr><td><code>-F</code></td>
388 <td>True if string is a valid file, accessible via all the server's
389 currently-configured access controls for that path. This uses an
390 internal subrequest to do the check, so use it with care - it can
391 impact your server's performance!</td><td></td></tr>
392 <tr><td><code>-U</code></td>
393 <td>True if string is a valid URL, accessible via all the server's
394 currently-configured access controls for that path. This uses an
395 internal subrequest to do the check, so use it with care - it can
396 impact your server's performance!</td><td></td></tr>
397 <tr><td><code>-A</code></td>
398 <td>Alias for <code>-U</code></td><td></td></tr>
399 <tr><td><code>-n</code></td>
400 <td>True if string is not empty</td><td></td></tr>
401 <tr><td><code>-z</code></td>
402 <td>True if string is empty</td><td></td></tr>
403 <tr><td><code>-T</code></td>
404 <td>False if string is empty, "<code>0</code>", "<code>off</code>",
405 "<code>false</code>", or "<code>no</code>" (case insensitive).
406 True otherwise.</td><td></td></tr>
407 <tr><td><code>-R</code></td>
408 <td>Same as "<code>%{REMOTE_ADDR} -ipmatch ...</code>", but more efficient
412 <p>The operators marked as "restricted" are not available in some modules
413 like <module>mod_include</module>.</p>
416 <section id="functions">
417 <title>Functions</title>
419 <p>Normal string-valued functions take one string as argument and return
420 a string. Functions names are not case sensitive.
421 Modules may register additional functions.</p>
423 <table border="1" style="zebra">
424 <columnspec><column width=".2"/><column width=".8"/></columnspec>
426 <tr><th>Name</th><th>Description</th><th>Restricted</th></tr>
427 <tr><td><code>req</code>, <code>http</code></td>
428 <td>Get HTTP request header</td><td></td></tr>
429 <tr><td><code>resp</code></td>
430 <td>Get HTTP response header</td><td></td></tr>
431 <tr><td><code>reqenv</code></td>
432 <td>Lookup request environment variable</td><td></td></tr>
433 <tr><td><code>osenv</code></td>
434 <td>Lookup operating system environment variable</td><td></td></tr>
435 <tr><td><code>note</code></td>
436 <td>Lookup request note</td><td></td></tr>
437 <tr><td><code>env</code></td>
438 <td>Return first match of <code>note</code>, <code>reqenv</code>,
439 <code>osenv</code></td><td></td></tr>
440 <tr><td><code>tolower</code></td>
441 <td>Convert string to lower case</td><td></td></tr>
442 <tr><td><code>toupper</code></td>
443 <td>Convert string to uppser case</td><td></td></tr>
444 <tr><td><code>escape</code></td>
445 <td>Escape special characters in %hex encoding</td><td></td></tr>
446 <tr><td><code>unescape</code></td>
447 <td>Unescape %hex encoded string, leaving encoded slashes alone;
448 return empty string if %00 is found</td><td></td></tr>
449 <tr><td><code>file</code></td>
450 <td>Read contents from a file</td><td>yes</td></tr>
451 <tr><td><code>filesize</code></td>
452 <td>Return size of a file (or 0 if file does not exist or is not
453 regular file)</td><td>yes</td></tr>
457 <p>The functions marked as "restricted" are not available in some modules
458 like <module>mod_include</module>.</p>
460 <p>In addition to string-valued functions, there are also list-valued functions which
461 take one string as argument and return a wordlist, i.e. a list of strings. The wordlist
462 can be used with the special <code>-in</code> operator.
463 Functions names are not case sensitive.
464 Modules may register additional functions.</p>
466 <p>There are no built-in list-valued functions. <module>mod_ssl</module>
467 provides <code>PeerExtList</code>. See the description of
468 <directive module="mod_ssl">SSLRequire</directive> for details
469 (but <code>PeerExtList</code> is also usable outside
470 of <directive module="mod_ssl">SSLRequire</directive>).</p>
474 <section id="examples">
476 <title>Example expressions</title>
477 <p>The following examples show how expressions might be used to evaluate requests:</p>
478 <!-- This section should probably be extended with more, useful examples -->
480 # Compare the host name to example.com and redirect to www.example.com if it matches<br />
481 <If "%{HTTP_HOST} == 'example.com'"><br />
483 Redirect permanent / http://www.example.com<br />
485 </If><br /><br />
486 # Force text/plain if requesting a file with the query string contains 'forcetext'<br />
487 <If "%{QUERY_STRING} =~ /forcetext/"><br />
489 ForceType text/plain<br />
491 </If><br /><br />
492 # Only allow access to this content during business hours<br />
493 <Directory "/foo/bar/business"><br />
495 Require expr %{TIME_HOUR} >= 9 && %{TIME_HOUR} <= 17 <br />
504 <table border="1" style="zebra">
505 <columnspec><column width=".2"/><column width=".2"/><column width=".6"/></columnspec>
507 <tr><th>Name</th><th>Alternative</th> <th>Description</th></tr>
508 <tr><td><code>-in</code></td>
509 <td><code>in</code></td>
510 <td>string contained in string list</td></tr>
511 <tr><td><code>/regexp/</code></td>
512 <td><code>m#regexp#</code></td>
513 <td>Regular expression (the second form allows different delimiters than /)</td></tr>
514 <tr><td><code>/regexp/i</code></td>
515 <td><code>m#regexp#i</code></td>
516 <td>Case insensitive regular expression</td></tr>
517 <tr><td><code>$0 ... $9</code></td>
519 <td>Regular expression backreferences</td></tr>
522 <section id="rebackref">
523 <title>Regular expression backreferences</title>
524 <p>The strings <code>$0</code> ... <code>$9</code> allow to reference
525 the capture groups from a previously executed, successfully
526 matching regular expressions. They can normally only be used in the
527 same expression as the matching regex, but some modules allow special
533 <section id="sslrequire">
534 <title>Comparison with SSLRequire</title>
535 <p>The <em>ap_expr</em> syntax is mostly a superset of the syntax of the
536 deprecated <directive module="mod_ssl">SSLRequire</directive> directive.
537 The differences are described in <directive
538 module="mod_ssl">SSLRequire</directive>'s documentation.</p>