This module provides a filter which will process files before they are sent to the client. The processing is controlled by specially formated SGML comments, referred to as elements. These elements allow conditional text, the inclusion other files or programs, as well as the setting and printing of environment variables.
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:
The following directive must be given for the directories
containing the shtml files (typically in a
<Directory> section, but this directive is
also valid .htaccess files if AllowOverride
Options is set):
For backwards compatibility, the server-parsed
handler also activates the
INCLUDES filter. As well, Apache will activate the INCLUDES
filter for any document with mime type
text/x-server-parsed-html or
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.
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; 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.
The allowed elements are:
bytes
for a count in bytes, or abbrev for a count
in Kb or Mb as appropriate.strftime(3) library routine when printing
dates.(none). Any dates printed are subject to the
currently configured timefmt. Attributes:
echo element,
the default is set to "entity", resulting in entity
encoding (which is appropriate in the context of a
block-level HTML element, eg. a paragraph of text). This
can be changed by adding an encoding
attribute, which will remain in effect until the next
encoding attribute is encountered or the
element ends, whichever comes first. Note that the
encoding attribute must precede the
corresponding var attribute to be effective,
and that 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. Apache 1.3.12 and
above; previous versions do no encoding.The CGI script is given the PATH_INFO and 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.
For example:
<!--#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.
The include
virtual element should be
used in preference to exec cgi. In particular,
if you need to pass additional arguments to a CGI program,
using the query string, this cannot be done with exec
cgi, but can be done with include
virtual, as shown here:
<!--#include virtual="/cgi-bin/example.cgi?argument=value" -->
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
virtual is almost always
prefered to using either #exec cgi or #exec
cmd. The former (#include virtual) used 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 exec directive, 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" -->
sizefmt format specification.
Attributes:
timefmt format
specification. The attributes are the same as for the
fsize command.An attribute defines the location of the document; the inclusion is done for each attribute given to the include command. The valid attributes are:
../, 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.
The virtual attribute should always be used
in preference to this one.The value is a (%-encoded) URL relative to the current document being parsed. 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 virtual should be used in preference
to exec cgi to include the output of CGI
programs into an HTML document.
This prints out a listing of all existing variables and
their values. Starting with Apache 1.3.12, special characters
are entity encoded (see the echo element for details)
before being output. There are no attributes.
For example:
<!--#printenv -->
The printenv element is available only in Apache 1.2 and above.
For example: <!--#set var="category" value="help"
-->
The set element is available only in Apache 1.2 and above.
echo command, for
if and elif, and to any program
invoked by the document.
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, 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}_${REQUEST_METHOD}" -->
This will result in the Zed variable being set to "X_Y" if REMOTE_HOST is "X" and REQUEST_METHOD is "Y".
EXAMPLE: the below example will print "in foo" if the DOCUMENT_URI is /foo/file.html, "in bar" if it is /bar/file.html and "in neither" otherwise:
<!--#if expr="\"$DOCUMENT_URI\" = \"/foo/file.html\"" -->
in foo
<!--#elif expr="\"$DOCUMENT_URI\" = \"/bar/file.html\"" -->
in bar
<!--#else -->
in neither
<!--#endif -->
<!--#if expr="test_condition" -->
<!--#elif expr="test_condition" -->
<!--#else -->
<!--#endif -->
The if element works like an
if statement in a programming language. The test condition is
evaluated and if the result is true, then the text until the
next elif,
else. or
endif element is included in the
output stream.
The elif or
else statements are be used the
put text into the output stream if the original test_condition
was false. These elements are optional.
The endif element ends the
if element and is required.
test_condition is one of the following:
"=" and "!=" bind more tightly than "&&" and "||". "!" binds most tightly. Thus, the following are equivalent:
<!--#if expr="$a = test1 && $b = test2" -->
<!--#if expr="($a = test1) && ($b = test2)" -->
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
'string1 string2' results in string1 string2
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.
This directive changes the string that mod_include looks for to mark the end of a include command.
The 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.
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 have 2 servers parsing the output of a file each processing different commands (possibly at different times).
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.
The XBitHack directives 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:
on but also test the group-execute bit.
If it is set, then set the Last-modified date 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.
Note: you would not want to use the full
option, unless you assure the group-execute bit is unset for
every SSI script which might #include a CGI
or otherwise produces different output on each hit (or could
potentially change on subsequent requests).