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Apache模塊 mod_include
| 說明 | 實現(xiàn)服務(wù)端包含文檔(SSI)處理 |
|---|---|
| 狀態(tài) | 基本(B) |
| 模塊名 | include_module |
| 源文件 | mod_include.c |
| 兼容性 | Implemented as an output filter since Apache 2.0 |
概述
This module provides a filter which will process files before they are sent to the client. The processing is controlled by specially formatted SGML comments, referred to as elements. These elements allow conditional text, the inclusion of other files or programs, as well as the setting and printing of environment variables.
Enabling Server-Side Includes
Server Side Includes are implemented by the
INCLUDES filter. If
documents containing server-side include directives are given
the extension .shtml, the following directives will make Apache
parse them and assign the resulting document the mime type of
text/html:
AddType text/html .shtml
AddOutputFilter INCLUDES .shtml
The following directive must be given for the directories
containing the shtml files (typically in a
<Directory> section,
but this directive is also valid in .htaccess files if
AllowOverride Options
is set):
Options +Includes
For backwards compatibility, the server-parsed
處理器 also activates the
INCLUDES filter. As well, Apache will activate the INCLUDES
filter for any document with mime type
text/x-server-parsed-html或text/x-server-parsed-html3 (and the resulting
output will have the mime type text/html).
For more information, see our Tutorial on Server Side Includes.
PATH_INFO with Server Side Includes
Files processed for server-side includes no longer accept
requests with PATH_INFO (trailing pathname information)
by default. You can use the AcceptPathInfo directive to
configure the server to accept requests with PATH_INFO.
Basic Elements
The document is parsed as an HTML document, with special commands embedded as SGML comments. A command has the syntax:
<!--#element attribute=value
attribute=value ... -->
The value will often be enclosed in double quotes, but single
quotes (') and backticks (`) are also
possible. Many commands only allow a single attribute-value pair.
Note that the comment terminator (-->) should be
preceded by whitespace to ensure that it isn't considered part of
an SSI token. Note that the leading <!--# is one
token and may not contain any whitespaces.
The allowed elements are listed in the following table:
| Element | Description |
|---|---|
config |
configure output formats |
echo |
print variables |
exec |
execute external programs |
fsize |
print size of a file |
flastmod |
print last modification time of a file |
include |
include a file |
printenv |
print all available variables |
set |
set a value of a variable |
SSI elements may be defined by modules other than
mod_include. In fact, the exec element is provided by
mod_cgi, and will only be available if this
module is loaded.
The config Element
This command controls various aspects of the parsing. The valid attributes are:
-
echomsg(Apache 2.1 and later) - The value is a message that is sent back to the
client if the
echoelement attempts to echo an undefined variable. This overrides anySSIUndefinedEchodirectives. errmsg- The value is a message that is sent back to the
client if an error occurs while parsing the
document. This overrides any
SSIErrorMsgdirectives. sizefmt- The value sets the format to be used which displaying
the size of a file. Valid values are
bytesfor a count in bytes, orabbrevfor a count in Kb or Mb as appropriate, for example a size of 1024 bytes will be printed as "1K". timefmt- The value is a string to be used by the
strftime(3)library routine when printing dates.
The echo Element
This command prints one of the include
variables, defined below. If the variable is unset, the result is
determined by the SSIUndefinedEcho directive. Any dates printed are
subject to the currently configured timefmt.
Attributes:
var- The value is the name of the variable to print.
encoding-
Specifies how Apache should encode special characters contained in the variable before outputting them. If set to
none, no encoding will be done. If set tourl, then URL encoding (also known as %-encoding; this is appropriate for use within URLs in links, etc.) will be performed. At the start of anechoelement, the default is set toentity, resulting in entity encoding (which is appropriate in the context of a block-level HTML element, 例如， a paragraph of text). This can be changed by adding anencodingattribute, which will remain in effect until the nextencodingattribute is encountered or the element ends, whichever comes first.encodingattribute must precede the correspondingvarattribute to be effective, and only special characters as defined in the ISO-8859-1 character encoding will be encoded. This encoding process may not have the desired result if a different character encoding is in use.In order to avoid cross-site scripting issues, you should always encode user supplied data.
The exec Element
exec command executes a given shell command or
CGI script. It requires mod_cgi to be present
in the server. If Options
IncludesNOEXEC is set, this command is completely
disabled. The valid attributes are:
cgi-
The value specifies a (%-encoded) URL-path to the CGI script. If the path does not begin with a slash (/), then it is taken to be relative to the current document. The document referenced by this path is invoked as a CGI script, even if the server would not normally recognize it as such. However, the directory containing the script must be enabled for CGI scripts (with
ScriptAlias或OptionsExecCGI).The CGI script is given the
PATH_INFOand query string (QUERY_STRING) of the original request from the client; these cannot be specified in the URL path. The include variables will be available to the script in addition to the standard CGI environment.示例
<!--#exec cgi="/cgi-bin/example.cgi" -->If the script returns a
Location:header instead of output, then this will be translated into an HTML anchor.include virtualelement should be used in preference toexec cgi. In particular, if you need to pass additional arguments to a CGI program, using the query string, this cannot be done withexec cgi, but can be done withinclude virtual, as shown here:<!--#include virtual="/cgi-bin/example.cgi?argument=value" --> cmd-
The server will execute the given string using
/bin/sh. The include variables are available to the command, in addition to the usual set of CGI variables.The use of
#include virtualis almost always prefered to using either#exec cgi或#exec cmd. The former (#include virtual) uses the standard Apache sub-request mechanism to include files or scripts. It is much better tested and maintained.In addition, on some platforms, like Win32, and on unix when using suexec, you cannot pass arguments to a command in an
execdirective, or otherwise include spaces in the command. Thus, while the following will work under a non-suexec configuration on unix, it will not produce the desired result under Win32, or when running suexec:<!--#exec cmd="perl /path/to/perlscript arg1 arg2" -->
The fsize Element
This command prints the size of the specified file, subject
to the sizefmt format specification. Attributes:
file- The value is a path relative to the directory containing the current document being parsed.
virtual- The value is a (%-encoded) URL-path. If it does not begin with a slash (/) then it is taken to be relative to the current document. Note, that this does not print the size of any CGI output, but the size of the CGI script itself.
The flastmod Element
This command prints the last modification date of the
specified file, subject to the timefmt format
specification. The attributes are the same as for the
fsize command.
The include Element
This command inserts the text of another document or file
into the parsed file. Any included file is subject to the usual
access control. If the directory containing the parsed file has
Options
IncludesNOEXEC set, then only documents with a text
MIME-type (text/plain, text/html etc.) will be included. Otherwise CGI
scripts are invoked as normal using the complete URL given in
the command, including any query string.
An attribute defines the location of the document; the inclusion is done for each attribute given to the include command. The valid attributes are:
file- The value is a path relative to the directory
containing the current document being parsed. It cannot
contain
../, nor can it be an absolute path. Therefore, you cannot include files that are outside of the document root, or above the current document in the directory structure. Thevirtualattribute should always be used in preference to this one. virtual-
The value is a (%-encoded) URL-path. The URL cannot contain a scheme or hostname, only a path and an optional query string. If it does not begin with a slash (/) then it is taken to be relative to the current document.
A URL is constructed from the attribute, and the output the server would return if the URL were accessed by the client is included in the parsed output. Thus included files can be nested.
If the specified URL is a CGI program, the program will be executed and its output inserted in place of the directive in the parsed file. You may include a query string in a CGI url:
<!--#include virtual="/cgi-bin/example.cgi?argument=value" -->include virtualshould be used in preference toexec cgito include the output of CGI programs into an HTML document.
The printenv Element
This prints out a listing of all existing variables and
their values. Special characters are entity encoded (see the echo element for details)
before being output. There are no attributes.
示例
<!--#printenv -->
The set Element
This sets the value of a variable. Attributes:
var- The name of the variable to set.
value- The value to give a variable.
示例
<!--#set var="category" value="help" -->
Include Variables
In addition to the variables in the standard CGI environment,
these are available for the echo command, for
if和elif, and to any program
invoked by the document.
DATE_GMT- The current date in Greenwich Mean Time.
DATE_LOCAL- The current date in the local time zone.
DOCUMENT_NAME- The filename (excluding directories) of the document requested by the user.
DOCUMENT_URI- The (%-decoded) URL path of the document requested by the user. Note that in the case of nested include files, this is not the URL for the current document.
LAST_MODIFIED- The last modification date of the document requested by the user.
QUERY_STRING_UNESCAPED- If a query string is present, this variable contains the
(%-decoded) query string, which is escaped for shell
usage (special characters like
&etc. are preceded by backslashes).
Variable Substitution
Variable substitution is done within quoted strings in most
cases where they may reasonably occur as an argument to an SSI
directive. This includes the config, exec, flastmod, fsize, include, echo, and set
directives, as well as the arguments to conditional operators.
You can insert a literal dollar sign into the string using backslash
quoting:
<!--#if expr="$a = \$test" -->
If a variable reference needs to be substituted in the middle of a character sequence that might otherwise be considered a valid identifier in its own right, it can be disambiguated by enclosing the reference in braces, a la shell substitution:
<!--#set var="Zed" value="${REMOTE_HOST}_${REQUEST_METHOD}" -->
This will result in the Zed variable being set
to "X_Y" if REMOTE_HOST is
"X" and REQUEST_METHOD is
"Y".
The below example will print "in foo" if the
DOCUMENT_URI is /foo/file.html, "in bar"
if it is /bar/file.html and "in neither" otherwise:
<!--#if expr='"$DOCUMENT_URI" = "/foo/file.html"' -->
in foo
<!--#elif expr='"$DOCUMENT_URI" = "/bar/file.html"' -->
in bar
<!--#else -->
in neither
<!--#endif -->
Flow Control Elements
The basic flow control elements are:
<!--#if expr="test_condition" -->
<!--#elif expr="test_condition" -->
<!--#else -->
<!--#endif -->
if element works like an if statement in a
programming language. The test condition is evaluated and if
the result is true, then the text until the next elif, else或endif element is included in the
output stream.
elif或else statements are be used
to put text into the output stream if the original
test_condition was false. These elements are optional.
endif element ends the if element
and is required.
test_condition is one of the following:
string- true if string is not empty
string1 = string2
string1 == string2
string1 != string2-
Compare string1 with string2. If string2 has the form
/string2/then it is treated as a regular expression. Regular expressions are implemented by the PCRE engine and have the same syntax as those in perl 5. Note that==is just an alias for=and behaves exactly the same way.If you are matching positive (
=或==), you can capture grouped parts of the regular expression. The captured parts are stored in the special variables$1..$9.示例
<!--#if expr="$QUERY_STRING = /^sid=([a-zA-Z0-9]+)/" -->
<!--#set var="session" value="$1" -->
<!--#endif --> string1 < string2
string1 <= string2
string1 > string2
string1 >= string2- Compare string1 with string2. Note, that
strings are compared literally (using
strcmp(3)). Therefore the string "100" is less than "20". ( test_condition )- true if test_condition is true
! test_condition- true if test_condition is false
test_condition1 && test_condition2- true if both test_condition1和test_condition2 are true
test_condition1 || test_condition2- true if either test_condition1或test_condition2 is true
"=" and "!=" bind more tightly than
"&&" and "||". "!" binds
most tightly. Thus, the following are equivalent:
<!--#if expr="$a = test1 && $b = test2" -->
<!--#if expr="($a = test1) && ($b = test2)" -->
The boolean operators &&和||
share the same priority. So if you want to bind such an operator more
tightly, you should use parentheses.
Anything that's not recognized as a variable or an operator
is treated as a string. Strings can also be quoted:
'string'. Unquoted strings can't contain whitespace
(blanks and tabs) because it is used to separate tokens such as
variables. If multiple strings are found in a row, they are
concatenated using blanks. So,
string1????string2 results in string1?string2
和'string1????string2' results in string1????string2.
Optimization of Boolean Expressions
If the expressions become more complex and slow down processing significantly, you can try to optimize them according to the evaluation rules:
- Expressions are evaluated from left to right
- Binary boolean operators (
&&和||) are short circuited wherever possible. In conclusion with the rule above that means,mod_includeevaluates at first the left expression. If the left result is sufficient to determine the end result, processing stops here. Otherwise it evaluates the right side and computes the end result from both left and right results. - Short circuit evaluation is turned off as long as there are regular
expressions to deal with. These must be evaluated to fill in the
backreference variables (
$1..$9).
If you want to look how a particular expression is handled, you can
recompile mod_include using the
-DDEBUG_INCLUDE compiler option. This inserts for every
parsed expression tokenizer information, the parse tree and how it is
evaluated into the output sent to the client.
SSIEndTag 指令
| 說明 | String that ends an include element |
|---|---|
| 語法 | SSIEndTag tag |
| 默認(rèn)值 | SSIEndTag "-->" |
| 作用域 | server config, virtual host |
| 狀態(tài) | 基本(B) |
| 模塊 | mod_include |
| 兼容性 | 僅在 Apache 2.0.30 及以后的版本中可用 |
This directive changes the string that mod_include
looks for to mark the end of an include element.
示例
SSIEndTag "%>"
參見
SSIStartTag
SSIErrorMsg 指令
| 說明 | Error message displayed when there is an SSI error |
|---|---|
| 語法 | SSIErrorMsg message |
| 默認(rèn)值 | SSIErrorMsg "[an error occurred while processing this
directive]" |
| 作用域 | server config, virtual host, directory, .htaccess |
| 覆蓋項 | All |
| 狀態(tài) | 基本(B) |
| 模塊 | mod_include |
| 兼容性 | 僅在 Apache 2.0.30 及以后的版本中可用 |
SSIErrorMsg directive changes the error
message displayed when mod_include encounters an
error. For production servers you may consider changing the default
error message to "<!-- Error -->" so that
the message is not presented to the user.
This directive has the same effect as the <!--#config
errmsg=message --> element.
示例
SSIErrorMsg "<!-- Error -->"
SSIStartTag 指令
| 說明 | String that starts an include element |
|---|---|
| 語法 | SSIStartTag tag |
| 默認(rèn)值 | SSIStartTag "<!--#" |
| 作用域 | server config, virtual host |
| 狀態(tài) | 基本(B) |
| 模塊 | mod_include |
| 兼容性 | 僅在 Apache 2.0.30 及以后的版本中可用 |
This directive changes the string that mod_include
looks for to mark an include element to process.
You may want to use this option if you have 2 servers parsing the output of a file each processing different commands (possibly at different times).
示例
SSIStartTag "<%"
SSIEndTag "%>"
The example given above, which also specifies a matching
SSIEndTag, will
allow you to use SSI directives as shown in the example
below:
SSI directives with alternate start and end tags
<%printenv %>
參見
SSIEndTag
SSITimeFormat 指令
| 說明 | Configures the format in which date strings are displayed |
|---|---|
| 語法 | SSITimeFormat formatstring |
| 默認(rèn)值 | SSITimeFormat "%A, %d-%b-%Y %H:%M:%S %Z" |
| 作用域 | server config, virtual host, directory, .htaccess |
| 覆蓋項 | All |
| 狀態(tài) | 基本(B) |
| 模塊 | mod_include |
| 兼容性 | 僅在 Apache 2.0.30 及以后的版本中可用 |
This directive changes the format in which date strings are displayed
when echoing DATE environment variables. The
formatstring is as in strftime(3) from the
C standard library.
This directive has the same effect as the <!--#config
timefmt=formatstring --> element.
示例
SSITimeFormat "%R, %B %d, %Y"
The above directive would cause times to be displayed in the format "22:26, June 14, 2002".
SSIUndefinedEcho 指令
| 說明 | String displayed when an unset variable is echoed |
|---|---|
| 語法 | SSIUndefinedEcho string |
| 默認(rèn)值 | SSIUndefinedEcho "(none)" |
| 作用域 | server config, virtual host, directory, .htaccess |
| 覆蓋項 | All |
| 狀態(tài) | 基本(B) |
| 模塊 | mod_include |
| 兼容性 | 僅在 Apache 2.0.34 及以后的版本中可用 |
This directive changes the string that mod_include
displays when a variable is not set and "echoed".
示例
SSIUndefinedEcho "<!-- undef -->"
XBitHack 指令
| 說明 | Parse SSI directives in files with the execute bit set |
|---|---|
| 語法 | XBitHack on|off|full |
| 默認(rèn)值 | XBitHack off |
| 作用域 | server config, virtual host, directory, .htaccess |
| 覆蓋項 | Options |
| 狀態(tài) | 基本(B) |
| 模塊 | mod_include |
XBitHack directive controls the parsing
of ordinary html documents. This directive only affects files associated
with the MIME-type text/html. XBitHack can take on the following values:
off- No special treatment of executable files.
on- Any
text/htmlfile that has the user-execute bit set will be treated as a server-parsed html document. full- As for
onbut also test the group-execute bit. If it is set, then set theLast-modifieddate of the returned file to be the last modified time of the file. If it is not set, then no last-modified date is sent. Setting this bit allows clients and proxies to cache the result of the request.注意
You would not want to use the full option, unless you assure the group-execute bit is unset for every SSI script which might
#includea CGI or otherwise produces different output on each hit (or could potentially change on subsequent requests).