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Apache HTTP Server Version 1.3
Module mod_include
This module provides for documents with Server Side Includes (SSI).
Status:
Base
Source
File: mod_include.c
Module
Identifier: includes_module
Summary
This module provides a handler 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.
For an introduction to this topic, we also provide a
tutorial on Server Side Includes.
Directives
See also: Options and
AddHandler.
Enabling Server-Side Includes
Any document with handler of "server-parsed" will be parsed by this module, if the Includes
option is set. 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
AddHandler server-parsed .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 .htaccess
files if AllowOverride Options is set):
Options +Includes
Alternatively the XBitHack directive can be used to parse
normal (text/html) files, based on file permissions.
For backwards compatibility, documents with mime type text/x-server-parsed-html
or text/x-server-parsed-html3 will also be parsed (and the resulting output given
the mime type text/html).
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; 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:
- config
- This command controls various aspects of the parsing. The valid attributes are:
- errmsg
- The value is a message that is sent back to the client if an error occurs whilst
parsing the document.
- sizefmt
- The value sets the format to be used which displaying the size of a file. Valid
values are
bytes for a count in bytes, or abbrev for a count
in Kb or Mb as appropriate.
- timefmt
- The value is a string to be used by the
strftime(3) library routine
when printing dates.
- echo
- This command prints one of the
include variables, defined
below. If the variable is unset, it is printed as
(none). 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
to "url", then URL encoding (also known as %-encoding; this is appropriate
for use within URLs in links, etc.) will be performed. At the start of an
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.
- exec
- The exec command executes a given shell command or CGI script. The IncludesNOEXEC
Option disables this command
completely. The valid attributes are:
- cgi
- The value specifies a (%-encoded) URL relative path to the CGI script. If the path
does not begin with a (/), 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 or
the ExecCGI Option).
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" -->
- 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 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" -->
- fsize
- 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 relative to the current document being parsed.
If it does not begin with a slash (/) then it is taken to be relative to the current
document.
- flastmod
- 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.
- include
- 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 the
Option
IncludesNOEXEC set, and the including the document would cause a program to be executed,
then it will not be included; this prevents the execution of CGI scripts. 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. The virtual attribute should always
be used in preference to this one.
- virtual
-
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.
- printenv
-
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.
- set
- This sets the value of a variable. Attributes:
- var
- The name of the variable to set.
- value
- The value to give a variable.
For example: <!--#set var="category" value="help" -->
The set element is available only in Apache 1.2 and above.
In addition to the variables in the standard CGI environment, these are available for the echo
command, for if and 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 then URL for the current document.
- LAST_MODIFIED
- The last modification date of the document requested by the user.
- USER_NAME
- Contains the owner of the file which included it.
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, 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="$a = \$test" -->
If a variable reference needs to be substituted in the middle of a character sequence that
might otherwise be considered a valid identifier in its own right, it can be disambiguated by
enclosing the reference in braces, à la shell substitution:
<!--#set var="Zed" value="${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="\"$DOCUMENT_URI\" = \"/bar/file.html\"" -->
in bar
<!--#else -->
in neither
<!--#endif -->
These are available in Apache 1.2 and above. The basic flow control elements are:
<!--#if expr="test_condition" -->
<!--#elif expr="test_condition" -->
<!--#else -->
<!--#endif -->
The if element works like an if statement in a programming
language. The test condition is evaluated and if the result is true, then the text until the
next elif, else. or endif
element is included in the output stream.
The elif or else statements are
be used the put text into the output stream if the original test_condition was false. These
elements are optional.
The endif element ends the if
element and is required.
test_condition is one of the following:
- string
- true if string is not empty
- string1 = string2
string1 != string2
string1 < string2
string1 <= string2
string1 > string2
string1 >= string2
- Compare string1 with string 2. If string2 has the form /string/ then it is
compared as a regular expression. Regular expressions have the same syntax as those found
in the Unix egrep command.
- ( test_condition )
- true if test_condition is true
- ! test_condition
- true if test_condition is false
- test_condition1 && test_condition2
- true if both test_condition1 and test_condition2 are true
- test_condition1 || test_condition2
- true if either test_condition1 or test_condition2 is true
"=" and "!=" bind more tightly than "&&"
and "||". "!" binds most tightly. Thus, the following
are equivalent:
<!--#if expr="$a = test1 && $b = test2" -->
<!--#if expr="($a = test1) && ($b = test2)" -->
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
Using Server Side Includes for ErrorDocuments
There is a document
which describes how to use the features of mod_include to offer internationalized customized
server error documents.
Syntax:
XBitHack on|off|full
Default:
XBitHack off
Context:
server config, virtual host, directory, .htaccess
Override:
Options
Status:
Base
Module:
mod_include
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:
- off
- No special treatment of executable files.
- on
- Any file that has the user-execute bit set will be treated as a server-parsed html
document.
- full
- As for
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 this, for example, when you #include
a CGI that produces different output on each hit (or potentially depends on the hit).
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