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NetForge 1.0 Manual:   Filters

Filters are used for post-processing responses of HTTP responders. A filter can read the responder's output, mofidy the response headers and write a new response body.

The name under which a Filter is installed is interpreted as a MIME type. All responses with that content type are processed by the filter.

Currently only one filter is implemented:

SSIFilter (Server-Side Includes)

SSI Syntax

<!--#element attribute1=value1 attribute2=value2 ... -->

Note that there is a space before the end-of-comment mark "-->" but not between the beginning-of-comment mark "<!--" and the '#' sign that precedes the element name.

Attribute values

Example. The following command sets the variable FOO to the value $BAR = "BARVALUE" if the variable BAR has the value BARVALUE:

<!--#set var=FOO value="\$BAR = \"${BAR}\"" -->

Variables

DATE_GMT	The current time in Greenwich Mean Time.
DATE_LOCAL	The current time in the server's local time zone.
DOCUMENT_NAME	The name of the resource that was requested by the client, without path (i.e. the URL-decoded part of the Request-URI between the last slash and an eventual option part).
DOCUMENT_PATH	The URL-decoded Request-URI (without an eventual option part).
LAST_MODIFIED	The last modification date of the requested resource if available, otherwise undefined.

Evaluating or printing an undefined variable results in the string "(none)". See below for descriptions of the SSI commands set, echo and printenv which deal with variables.

Commands

• if, elif, else, endif: These are the control flow commands with the usual semantics. Currently they can not be nested. else and endif don't have any attributes. if and elif have one attribute:

  expr

  A boolean expression which can have one of the following forms: string1 = string2 string1 != string2 string1 > string2 string1 < string2 string1 >= string2 string1 <= string2 Compare string1 and string2. (expression) True if expression is true. !expression True if expression is false. Strings can be either tokens or (single-)quoted strings (e.g. 'string').

• config: Set a configuration option. Multiple options can be set with a single command (NetForge only). Attributes:

  errmsg	A message which is sent back to the client if an error occurs while parsing the SSI input.
  sizefmt	The format which is used to print file sizes. Valid values are "bytes" for a count in bytes and "abbrev" for a count in Kb or Mb (with a 'K' or 'M' suffix) as appropriate.
  timefmt	The format which is used to print dates. The value is a format string for the strftime(3) library function (minus some implementation-specific limitations) which is internally converted to a SimpleDateFormat format string. Use the javatimefmt attribute to set that string directly.
  javatimefmt	The format which is used to print dates. The value is a format string for the java.text.SimpleDateFormat class. NetForge only.

• echo: Print the value of a variable. Attributes:

  var	The variable's name.

• exec: Execute a shell command or request an internal URL and include the output in the response. Attributes:

  cgi

  A URL without a scheme, host name or option part. If it does not begin with a slash it is taken to be relative to the document being parsed. The option part of the user's original request is appended to the URL. The URL (which need not map to a CGI program) is then processed by the server. If the response contains a "Location" header, its value is printed as an HTML hyperlink, otherwise the response body is printed. The "include virtual" command should be used in preference to "exec cgi".

  cmd

  A command which is executed with a shell (as specified in the SSIFilter's configuration options). The SSI variables are passed to the shell process.

• fsize: Print the size of a file or resource in the format specified by the sizefmt configuration option (see config). Same attributes as include.

• flastmod: Print the modification date of a file or resource in the format specified by the timefmt or javatimefmt configuration option (see config). Same attributes as include.

• include: Include a file or resource in the response. Currently only one attribute / one included resource is allowed per command. Attributes:

  file	A path to the file. If it is not an absolute path in the local file system, it is interpreted as an NFile relative to the NFile which is associated with the document being parsed.
  virtual	A URL without a scheme or host name. If it does not begin with a slash it is taken to be relative to the document being parsed.

• printenv: Print out a list of all defined variables and their values. No attributes.

• set: Set the value of a variable. Attributes:

  var	The variable's name.
  value	The variable's new value.