The HTML pre-processor is used to provide dynamic information inside of an otherwise static, HTML (HyperText Markup Language) document. The HTTPd server provides this as internal functionality, scanning the input document for special pre-processor directives, which are replaced by dynamic information based upon the particular directive.
As of version 5.1 WASD SSI has been enhanced to provide flow-control statements, allowing blocks of the document to be conditionally processed, see 4.7 - Flow Control. These extensions allow quite versatile documents to be created without resorting to script processing.
Two documents are provided as examples of SSI processing.
By default the HTML pre-processor is invoked when the document file's extension is ".SHTML". As there is a significant overhead with pre-processed HTML compared to normal HTML, it should only be used when it serves a useful documentary purpose, and not just for the novelty.
Essential compatibility with OSU Server Side Includes is provided. This may ease any transition between the two. See 4.11 - OSU Compatibility for further information.
One effective use for pre-processed HTML is the creation of single virtual documents from two or more physical documents. That is, the pre-processed document is used to include multiple physical documents, that may even be independently administered, to return a composite document to the client. This is a relatively low-overhead activity as SSI goes, but because it is a dynamic document, without some extra considerations (see 4.2 - Last-Modified Information).
This provides an example of the efficient use of SSI processing to create virtual documents. Each page will comprise a header (containing the body tag and page header, etc), the document proper and a footer (containg the end-of-page information, modification date, and end-body tag, etc).
<HTML> <HEAD> <TITLE>Just an example!</TITLE> </HEAD> <!--#include virtual="header.shtml" --> <P> This is the document information. <P> Blah, blah, blah. <!--#include virtual="/web/common/footer.shtml" --> </HTML>
A more efficient variant places the document proper in its own, plain HTML file which is then #included (it is much, much, much more efficient for the server to throw a file at the network, than parse every character in one ;^)
<HTML> <HEAD> <TITLE>Just an example!</TITLE> </HEAD> <!--#include virtual="header.shtml" --> <!--#include virtual="example.html" --> <!--#include virtual="footer.shtml" --> </HTML>
This example provides a seemingly more convoluted, but very much more powerful configuration, that uses recursion to greatly simplify maintenance of common-layout documents for the end-user.
File 1; the document accessed via the browser URL, doesn't matter what its name is, this configuration is completely naming independent.
<!--#ssi
#if var={PARENT_FILE_NAME} eqs=""
#set var=TITLE value="Just an Example"
#include virtual="/web/common/template.shtml"
#else
#include virtual="document.html"
#endif
-->
File 2; the TEMPLATE.SHTML refered to by the first include above.
<!--#ssi
#include virtual="/web/common/header.shtml"
#include virtual="{DOCUMENT_ROOT}header.html" fmt="?"
#include virtual="{DOCUMENT_URI}"
#include virtual="{DOCUMENT_ROOT}footer.html" fmt="?"
#include virtual="/web/common/footer.shtml"
-->
File 3; the DOCUMENT.HTML refered to by the second include in file 1.
<P> This is just a <B>bunch of HTML</B>!
This is an explanation of how it works ...
The following link provides an example of a such a virtual document.
SSI documents generally contain dynamic elements, that is those that may change with each access to the document (e.g. current date/time). This makes evaluation of any document modification date difficult and so by default no "Last-Modified: timestamp" information is supplied against an SSI document. The potential efficiencies of having document timestamps, so that requests can be made for a document to be returned only if modified after a certain date/time ("If-Modified-Since: timestamp"), are significant against the CPU overheads of processing SSI documents.
WASD allows the document author to determine whether or not a last-modified header field should be generated for a particular document and which contributing file(s) should be used to determine it. This is done using the #modified directive. If a virtual document is made up of multiple source documents (files) each can be assessed using multiple virtual= or file= tags, the most recently modified will be used to determine if the virtual document has been modified, and also to generate the last-modified timestamp.
The if-modified-since tag compares the determined revision date/time of the document file(s) with any "If-Modified-Since:" timestamp supplied with the request. If the virtual document's revision date/time is the same or older than the request's then a not-modified (304 status) header is generated and sent to the client and document processing ceases. If more recent an appropriate "Last-Modified:" header field is added to the document and it continues to be processed.
If a request has a "Pragma: no-cache" field (as with Navigator's reload function) the document is always generated (this is consistent with general WASD behaviour). The following example illustrates the essential features.
<!--#ssi #modified #modified virtual="/web/common/header.shtml" #modified virtual="header.html" fmt="?" #modified virtual="index.html" fmt="?" #modified virtual="footer.html" fmt="?" #modified virtual="/web/common/footer.shtml" #modified if-modified-since -->
This construct should be placed at the very beginning of the SSI document, and certainly before there is any chance of output being sent to the browser. Once output to the client has occured there can be no change to the response header information (not unreasonably).
SSI preprocessed documents are dynamic in the sense that the information presented can be different every time the document is generated (e.g. if time directives are included). If it is important that each time the document is accessed it is regenerated then an HTML META tag can be included in the HTML header to cause the document to expire. This will result in the document being reloaded with each access. This can be accomplished two ways.
<!--#modified expires="Fri, 13 Jan 1978 14:00:00 GMT" -->An alternative, if the objective to to pre-expire the document, is to specify an expiry of zero. The is specially handled by the SSI engine. It adds an expiry response header field, plus cache-control header fields to suppress document caching (on compliant browsers).
<!--#modified expires="0" -->
The syntax follows closely that used by the other implementations, but some directives are tailored to the WASD and VMS environment. The directive is enclosed within an HTML comment and takes the form:
<!--#directive [[tag1="value"] [tag2="value"] ...] -->
A tag provides parameter information to the directive. A directive may have zero, one or more parameters. Values supplied with any tag may be literal or via variable substitution (see 4.6 - Variables. A value must be encolosed by quotation marks if it contains white-space.
A directive can be split over multiple lines provided the new line begins naturally on white-space within the directive. For example, this is correctly split
<!--#echo created[="<EMPHASIS>(time-format)"] -->while the following is not (and would produce an error)
<!--#echo creat ed[="<EMPHASIS>(time-format)"] -->
Directive and tag keywords are case insensitive. The tag value may or may not be case sensitive, depending upon the command/tag. Generally the effect of a command is to produce additional text to be inserted in the document, although it is possible to control the flow of processing in a document with decision structures.
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The #accesses directive allows the number of times the document has been accessed to be included. It does this by creating a counter file in the same location and using the same name with a dollar symbol appended to the type (extension). The count may be reset by deleting the file. This is an expensive function (in terms of file system activity) and so should be used appropriately. It can be disabled by server configuration. Three tags provide additional functionality:
<!--#accesses ordinal -->
Provides the count as 1st, 2nd, 3rd, 4th, 5th ... 10th, 11th, 12th ... 120th, 121st, 122nd, etc.
<!--#accesses since="text" -->
This tag includes the specified text immediately after the access count is displayed, then adds the creation date of the counter file.
<!--#accesses since="text" timefmt="[time-format]" -->Allows the time format of the since tag to be supplied, where time-format is specified according to 4.10 - Time Format.
The #config directive allows time and file size formats to be specified for all subsequent directives providing these values. Optional specifications for individual directives may still be made, and override, do not supercede, any specification made using a config directive. A config directive may be made once, or any number of times in a document, and applies until another is made, or until the end of the document.
<!--#config errmsg="string" -->
This directive allows the error message generated if a problem problem processing the SSI document occurs (e.g. miss-spelled directive) to be specified in the document.
<!--#config timefmt="time-format" -->Where time-format is specified according to 4.10 - Time Format.
<!--#config sizefmt="size-format" -->Where size-format is specified using the following keywords:
<!--#config trace="1|0" -->
Switches document processing trace on or off, intended for use when debugging more complex or flow-controlled SSI documents.
Output from a trace is colour-coded.
The following link provides an example of a document trace.
The #dir directive generates an Index of ... directory listing inside an HTML document. Apart from not generating a title (it is up to the pre-processed document to title, or otherwise caption, the listing) it provides all the functionality of the WASD HTTPd directory listing (see 3 - Directory Listing), including query string format control via the "par=" parameter (note that from the "?httpd=index" introducer used with directory listings is not necessary from SSI). It is an WASD HTTPd extension to pre-processed HTML.
Listing specified using a VMS file path.
<!--#dir file="file-name" [par="server-directive(s)"] -->
Listing specified using URL-style syntax.
<!--#dir virtual="path" [par="server-directive(s)"] -->
For example:
<!--#dir file="/wasd_root/src/httpd/" --> <!--#dir file="/wasd_root/src/httpd/*.c" par="layout=UL__S&nops=yes" -->
The #dcl directive executes a DCL command and incorporates the output into the processed document. It is an WASD HTTPd extension to the more common exec directive, which is also included.
By default, output from the DCL command has all HTML-forbidden characters (e.g. "<", "&") escaped before inclusion in the processed document. Thus command output cannot interfere with document markup, but nor can the DCL command provide HTML markup. This behaviour may be changed by appending the following tag to the directive:
type="text/html"
Some #dcl directives are for privileged documents only, documents defined as those being owned by the SYSTEM account, and not being world-writeable. The reason for this should be obvious. There are implicit security concerns about any document being able to execute any DCL command(s), even if it is being executed in a completely unprivileged process. Hence only innocuous commands are allowed in standard documents.
Execute the DCL "WRITE SYS$OUTPUT" command, using the specified parameter.
<!--#dcl say="hello." -->
Execute the DCL "SHOW" command, using the specified parameter.
<!--#dcl show="device/full tape1:" -->
Execute the DCL "DIRECTORY" command, using the supplied file specification. Qualifiers may be included in the optional "par" tag to control the format of the listing.
<!--#dcl dir="web:[000000]" --> <!--#dcl dir="web:[000000]" par="/nohead/notrail" --> <!--#dcl dir="web:[000000]" par="/size/date" -->
Execute the specified DCL command.
<!--#dcl exec="show device/full tape1:" -->
Execute the DCL command procedure specified as a VMS file path, with any specified parameters applied to the procedure.
<!--#dcl file="WASD_ROOT:[SHTML]TEST.COM" par="PARAM1 PARAM2" -->
Execute the DCL command procedure specified in URL-style syntax, with any specified parameters applied to the procedure.
<!--#dcl virtual="../shtml/test.com" par="PARAM1 PARAM2" -->
Execute the specified CGI script. The CGI response header is suppressed and only the response body is included in the document.
<!--#dcl cgi="/cgi-bin/calendar?2004" -->
The #echo directive incorporates the specified information into the processed document. Multiple tags may be used within the one directive.
Any SSI variable (e.g. CREATED), CGI variable (e.g. HTTP_USER_AGENT), or document assigned variable (e.g. EXAMPLE1), see 4.6 - Variables.
<!--#echo value={created} var={example1} -->
The date/time of the current document's creation.
<!--#echo created[="time-format"] -->
Include the current date/time.
<!--#echo date_local[="time-format"] -->
Include the current Greenwich Mean Time (UTC) date/time.
<!--#echo date_gmt[="time-format"] -->
The current document's URL-style path.
<!--#echo document_name -->
The current document's VMS file path.
<!--#echo file_name -->
Append the specified string to the response header (with correct carriage control). Should be used as early as possible in the SSI document.
<!--#echo header="Pragma: no-cache" --> <!--#echo header="X-Extension-Header: just an example!" -->
The date/time of the current document's last modification.
<!--#echo last_modified[="time-format"] -->
The #elif directive (else-if) allows blocks of HTML markup and SSI directives to be conditionally processed, see 4.7 - Flow Control and 4.5.14 - #IF. This directive effectively allows a case statement to be constructed.
<!--#elif var="[{variable}|literal" -->
The else directive allows blocks of HTML markup and SSI directives to be conditionally processed, see 4.7 - Flow Control. It is the default block after an "#if", "#orif" or "#elif".
<!--#else -->
The #endif directive marks the end of a block of document text being conditionally processed, see 4.7 - Flow Control.
<!--#endif -->
The #exec directive executes a DCL command and incorporates the output into the processed document. It is the VMS equivalent of the exec shell directive of some Unix implementations. It is implemented in the same way as the #DCL directive, and so the general detail of that directive applies. It supports both the cmd tag and the cgi tag, allowing execution of CGI scripts (the response header is absorbed).
<!--#exec cmd="show device/full tape1:" --> <!--#exec cgi="/cgi-bin/calendar?2004" -->
The exec directive is for privileged documents only, documents defined as those being owned by the SYSTEM account, and not being world-writeable. The reason for this should be obvious. There are implicit security concerns about any document being able to execute any DCL command(s), even if it is being executed in a completely unprivileged process.
The #exit directive causes the server to stop processing the current SSI file. If the current file was an #included SSI file, processing continues back with the parent file. Note that the #stop directive also is available, it stops processing of the entire virtual document.
<!--#exit -->
The #fcreated directive incorporates the creation date/time of a specified file/document into the processed document.
Document specified using a VMS file path.
<!--#fcreated file="file-name" [fmt="time-format"] -->
Document specified using URL-style syntax.
<!--#fcreated virtual="path" [fmt="time-format"] -->
The #flastmod directive incorporates the last modification date/time of a specified file/document into the processed document.
Document specified using a VMS file path.
<!--#flastmod file="file-name" [fmt="time-format"] -->
Document specified using URL-style syntax.
<!--#flastmod virtual="path" [fmt="time-format"] -->
The #fsize directive incorporates the size, in bytes, kbytes or Mbytes, of a specified file/document into the processed document.
Document specified using a VMS file path.
<!--#fsize file="file-name" [fmt="size-format"] -->
Document specified using URL-style syntax.
<!--#fsize virtual="path" [fmt="size-format"] -->
The #if directive allows blocks of HTML markup and SSI directives to be conditionally processed, see 4.7 - Flow Control.
Variable the decision will be based upon.
<!--#if var="[{variable}|literal]" -->
Is the string the same as in the variable?
If the variable is a number is it the same as this?
If the variable is a number is it greater than this?
If the variable is a number is it less than this?
Search the variable for this string. May contain the "*" wildcard, matching one or more characters, and the "%", matching any single character.
As in the following examples:
<!--#if value={DOCUMENT_URI} eqs="/wasd_root/doc/env/xssi.shtml" -->
<!--#if value={COUNT} lt=10 -->
<!--#if value="This is a test!" eqs={STRING} -->
<!--#if value={PATH_INFO} srch="*/env/*" -->
The #include directive incorporates the contents of a specified file/document into the processed document.
Include the contents of the document specified using a VMS file specification.
<!--#include file="file-name" -->
Include the contents of the document specified using URL-style syntax.
<!--#include virtual="path" -->
The contents of the specified file are included differently depending on the MIME content-type of the file. Files of text/html content-type (HTML documents) are included directly, and any HTML tags within them contribute to the markup of the document. Files of text/plain content-type (plain-text documents) are encapsulated in "<PRE></PRE>" tags and have all HTML-forbidden characters (e.g. "<", "&") escaped before inclusion in the processed document. An HTML file can be forced to be included as plain-text by using the following syntax:
<!--#include virtual="example.html" type="text/plain" -->
To "force" a file to be considered as text regardless of the actual content (as determined by the server from the file type), use on of the following depending on whether it should be rendered as plain or HTML text.
<!--#include virtual="example.html" content="text/plain" --> <!--#include virtual="example.html" content="text/html" -->
Other SSI files may be included and their content dynamically included in the resulting document. To prevent a recursive inclusion of documents the nesting level of SSI documents is limited to five.
The #modified directive allows a document author to control the "Last-Modified:"/"If-Modified-Since:"/"304 Not modified" behaviour of an SSI document. See 4.1 - Virtual Documents.
Get the last-modified date/time of the current document.
<!--#modified -->
Get the last-modified date/time of the document specified using VMS file specification.
<!--#modified file="file-name" -->
Get the last-modified date/time of the document specified using URL-style syntax.
<!--#modified virtual="path" -->
Compares any "If-Modified-Since:" request header timestamp to the revision date time obtained using file or virtual (most recent if multiple). If the document timestamp is more recent (has been modified) an appropriate "Last-Modified" response header field is generated and added to the response, and document processing continues. If it has not been modified a "304" response header is return (document not modified) and document processing stops.
<!--#modified if-modified-since -->
Adds a "Last-Modified:" response header field using a timestamp retrieved using file or virtual (note: unnecessary if the if-modified-since tag is used).
<!--#modified last-modified -->
Adds a "Expires:" response header field. The string literal should be a legitimate RFC-1123 date string. This can be used for pre-expiring documents (so they are always reloaded), set it to a date in the not-too-distant past (as in the example below). Of course it could also be used for setting the legitimate future expiry of documents.
<!--#modified expires="Fri, 13 Jan 1978 14:00:00 GMT" -->
The #orif directive (or-if) allows blocks of HTML markup and SSI directives to be conditionally processed, see 4.7 - Flow Control and 4.5.14 - #IF. In the absence of any real expression parser this directive allows a block to be processed if one of multiple conditions are met.
<!--#orif var="[{variable}|literal" -->
The #printenv directive prints a plain-text list of all SSI-specific, then CGI, then document-assigned variables (see 4.6 - Variables). This directive is intended for use when debugging flow-controlled SSI documents.
<!--#printenv -->
The following link uses the example SSI document WASD_ROOT:[DOC.ENV]XSSI.SHTML to demonstrate this.
xssi.shtml?httpd=ssi&printenv=yes&test1=one&test2=two&test3=three
The #set directive allows a user variable to be assigned or modified, see 4.6 - Variables.
<!--#set var="variable-name" value="whatever" -->
Variables are always stored as strings and have a finite but generally usable length. Some comparison tags provided in the flow-control directives treat the contents of variables as numbers. A numeric conversion is done at evaluation time.
The #ssi directive allows multiple SSI directives to be used without the requirement to enclose them in the normal HTML comment tags (i.e. <!-- -->). This helps reduce the clutter in an SSI document that uses the extended capabilities of variable assignment and flow control. Document HTML cannot be included between the opening and closing comment elements of the "#ssi" tag, although of course document output can be generated using the "#echo" tag.
<!--#ssi
#set var=HOUR value={DATE_LOCAL,12,2}
#if var={HOUR} lt=12
#set var=GREETING value="Good morning"
#elif var={HOUR} lt=19
#set var=GREETING value="Good afternoon"
#else
#set var=GREETING value="Good evening"
#endif
-->
The example SSI document WASD_ROOT:[DOC.ENV]XSSI.SHTML illustrates this concept.
The #stop directive causes the server to stop processing the virtual document. It can be used with flow control structures to conditionally process only part of a virtual document. Note that the #exit directive also is available, it stops processing of the current file (for nested #includes, etc.).
<!--#stop -->
The SSI processor maintains information about the server, date and time, request path, request parameters, etc., accessible via variable name. Although these server variables cannot be modified by the document the processor also allows the author to create and assign new document variables by name. SSI variables have global scope, with a small number of exceptions listed below. That is, the same set of variables are shared with the parent document by any other SSI documents #included, and any included by those, etc.
Local variables:
One other special-purpose variable, THE_FILE_NAME, see 4.9.1 - THE_FILE_NAME.
Server assigned variables comprise some SSI-specific as well as the same CGI variables available to CGI scripts. These may be found listed in the "CGI Scripting" chapter of the Technical Overview.
The following link provides a list of the SSI and CGI variables available to SSI documents.
Whenever a directive uses information from a tag (see 4.4 - Directive Syntax) values from variables may be substituted as as a whole or partial value. This is done using curly braces to delimit the variable name. For example
<!--#include virtual={FILENAME} -->
would include the file named by the contents of a variable named
"FILENAME". When using a variable in a tag it is not necessary to
enclose the tag parameter in quotation marks unless there is additional
literal text. Variables may also be used within literal strings,
producing a compound, resultant string, as in the following example
<!--#echo var="Hello {REMOTE_HOST}, time here is {LOCAL_TIME}" -->
Variables are considered numeric when they begin with a digit. Those beginning with an alphabetic are considered to have a numeric value of zero.
Variables are considered to be boolean false if empty and true when not empty.
It is also possible to extract substrings from variables using the following syntax,
{variable-name,start-index,count}
where the start-index begins with the zeroth character and numbers up to the last character in the string, and count may be zero or any positive number. If only one number is supplied it is regarded as a count and the string is extracted from the zeroth character.
To illustrate,
<!--#set var=EXAMPLE value="This is an example!" -->
<!--#echo "{EXAMPLE,2}at was {EXAMPLE,8,999}" -->
would output
That was an example!
{variable-name[,start-index],count]],length}
For example
<!--#set var=EXAMPLE value="This is an example!" -->
<!--#echo "\"{EXAMPLE}\" is {EXAMPLE,length} characters long." -->
<!--#echo "\"{EXAMPLE,5,2}\" is {EXAMPLE,5,2,length} characters long!" -->
would output
"This is an example!" is 19 characters long. "is" is 2 characters long!
var={variable-name,exists}
For example
<!--#set var=BOGUS_VARIABLE value="irrelevant" -->
<!--#if var={BOGUS_VARIABLE,exists} -->
"BOGUS_VARIABLE" exists!
<!--#else -->
"BOGUS_VARIABLE" does NOT exist!
<!--#endif -->
The example SSI document
WASD_ROOT:[DOC.ENV]XSSI.SHTML
illustrates these concepts.
4.7 - Flow Control
WASD SSI allows blocks of document to be conditionally processed. This uses constructs in a similar way to any programming language. The emphasis has been on simplicity and speed of processing. No complex expression parser is provided. Despite this, complex document constructs can be implemented. Flow control structures may be nested up to eight levels.
The "#if", "#orif" and "#elif" directives must provide an evaluation. This can be single variable, which if numeric and non-zero is considered true, if zero if false, or can be a string, which if empty is false, and if not empty is true. Tests can be made against the variable which when evaluated return a true or false. Multiple tests may be made against the one variable, or against more than one variable. Multiple tests act as a logical AND of the results and terminate when the first fails.
Any evaluation can have the result negated by prefixing it with an exclamation point. For instance, the first of these examples would produce a false result, the second true.
<!--#if value="test" !eqs="test" --> <!--#if value=20 !lt=10 -->
The following is a simple example illustration of variable setting, use of variable substrings, and conditional processing of document blocks.
<!--##config trace=1 -->
<HTML>
<!--#set var=HOUR value={DATE_LOCAL,12,5} -->
<!--#if var={HOUR} lt=12 -->
<!--#set var=GREETING value="Good morning" -->
<!--#elif var={HOUR} lt=19 -->
<!--#set var=GREETING value="Good afternoon" -->
<!--#else -->
<!--#set var=GREETING value="Good evening" -->
<!--#endif -->
<HEAD>
<TITLE><!--#echo var={GREETING} -->
<!--#echo var="{REMOTE_HOST}!" --></TITLE>
</HEAD>
<BODY>
<H1>Simple XSSI Demonstration</H1>
<!--#echo var={GREETING} --> <!--#echo var={REMOTE_HOST} -->,
the time here is <!--#echo var={DATE_LOCAL,12,5} -->.
<!--#if var={REMOTE_HOST} eqs={REMOTE_ADDR} -->
(Sorry, I do not know your name, DNS lookup must be disabled!)
<!--#endif -->
</BODY>
</HTML>
The example SSI document WASD_ROOT:[DOC.ENV]XSSI.SHTML further illustrates these concepts.
A query string may be passed to an SSI document in much the same way as to a CGI script. In this way the behaviour of the document can be varied in accordance to information explicitly passed to it when accessed. To prevent the server's default query engine being given the request precede any query string with "?httpd=ssi". The server detects this and passes the request instead to the SSI processor. Just append the desired query string components to this as if they were form elements. For example:
?httpd=ssi&printenv=no ?httpd=ssi&printenv=yes ?httpd=ssi&trace=yes&test2=one&test2=two&test3=three
The following link uses the example SSI document
WASD_ROOT:[DOC.ENV]XSSI.SHTML
to demonstrate this. Look for the (FORM_TEST1=one), etc.
xssi.shtml?httpd=ssi&printenv=yes&test1=one&test2=two&test3=three
Documents may be specified using either the "FILE" or "VIRTUAL" tags.
The "FILE" tag expects an absolute VMS file specification.
The "VIRTUAL" tag expects an URL-style path to a document. This can be an absolute or relative path. See 2.3 - Document Specification for further details.
Generally, when an error are encountered document processing halts and and an error report is generated. For some common circumstances, in particular the existance or not of a particular file, may require an alternative action. For file activities (e.g. #include, #flastmod, #created, #fsize) the optional fmt="" tag provides some measure of control on error behaviour. If the format string begins with a "?" files not found are not reported as errors and processing continues. Other file systems errors, such as directory not found, syntax errors, etc., are always reported.
Every time a file is accessed (e.g. #include, #flastmod) the server variable THE_FILE_NAME gets set to that name if successful, or reset to empty if unsuccessful. This variable can be checked to determine success or otherwise.
<!--#fcreated virtual="TEST.TXT" fmt="?" -->
<!--#if var={THE_FILE_NAME} eqs="" -->
File does not exist!
<!--#else -->
File exists!
<!--#endif -->
Whenever a time directive is used an optional tag can be included to specify the format of the output. The default looks a little VMS-ish. If a format specification is made it must confirm to the C programming language function strftime().
The format specifier follows a similar syntax to the C standard library printf() family of functions, where conversion specifiers are introduced by percentage symbols. Here are some example uses:
The date is <!--#echo date_local fmt="%d/%m/%y" -->. The time is <!--#echo date_local fmt="%r" -->. The day-of-the-week is <!--#echo date_local fmt="%A" -->.
A problem with any supplied time formatting specification will be reported.
The following table provides the general conversion specifiers. For futher information on the formatting process refer to a C programming library document on the strftime() function.
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Essential compatibility with OSU Server Side Includes directives is provided. This is intended to ease any transition to WASD, as existing SSI documents will not need to be changed unless any of the WASD capabilities are required. To provide transparent processing of OSU ".HTMLX" files ensure the following WASD configuration is in place.
In HTTPD$CONFIG file:
[AddType] .HTMLX text/x-shtml - OSU SSI HTML
Note that the content description must contain the string "OSU" to activate some compliancy behaviours.
In HTTPD$MAP file:
redirect /*.*.htmlx /*.htmlx?httpd=ssi&__part=*
This provides a mechanism for the OSU part-document facility. (Yes, the "__part" has two leading underscores!)
The following OSU directives are provided specifically for OSU compatibility, although there is no reason why most of these may not also be deployed in general WASD SSI documents if there is a requirement. Note that these are OSU-specifics, other OSU directives are provided by the standard WASD SSI engine.
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If WASD is configured for OSU SSI compatibility the following link provides an online demonstration as well as further explanation of the OSU SSI engine using an OSU preprocessor document from the distribution (included within copyright compliance).
/wasd_root/src/osu/preproc.htmlx
How do we know WASD is processing it? Look for the #echo var="GETENV=SYS$REM_ID" towards the end of the document. It should indicate "[VARIABLE_DOES_NOT_EXIST!]" because it's attempting to output a DECnet-related logical name!
The OSU processor allows for delimited subsections of an #included document, or a URL referenced document for that matter, to be included in the output. This is supported, but only for compatibility. It is only enabled for ".HTMLX" documents and if otherwise used may interact unexpectedly with WASD SSI flow-control.
It is possible to have script output passed back through the SSI engine for markup. This approach might allow script output to automatically be wrapped in standard site headers and footers for example. Essentially the script must output an SSI-markup response body and include in the otherwise standard CGI response header a field containing "Script-Control: X-content-handler=SSI". The following example in DCL show the essential elements of such a script.
$ say = "write sys$output" $ say "Status: 200" $ say "Script-Control: X-content-handler=SSI"" $ say "" $ say "<HTML>" $ say "<HEAD>" $ say "<TITLE>Example of X-content-handler=SSI</TITLE>" $ say "</HEAD>" $ say "<BODY>" $ say "<!--#include virtual=""/site/header.html"" -->" $ say "<H1>Example of X-content-handler:SSI</H1>" $ say "Hi there <!--#echo var=""WWW_REMOTE_HOST"" -->" $ say "<!--#include virtual=""/site/footer.html"" -->" $ say "</BODY>" $ say "</HTML>"