Apache HTTP Server Version 1.3
Module mod_include
This module is contained in the mod_include.c file, and
is compiled in by default. It provides for server-parsed html
documents. Several directives beyond the original NCSA definition have been
included in Apache 1.2 - these are flagged below with the phrase
"Apache 1.2 and above". Of particular significance are the new flow
control directives documented at the bottom.
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.
- 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.
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.
- cmd
- The server will execute the given string using
/bin/sh.
The include variables are available to the command.
- 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. 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.
- printenv
- This prints out a listing of all existing variables and their values.
No attributes.
- For example:
<!--#printenv -->
- 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" -->
- Apache 1.2 and above.
Include Variables
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.
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
Directives
Syntax: XBitHack status
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.
Status can have 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).
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.
Apache HTTP Server Version 1.3
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