IFILTER

WHAT THEY ARE

IFilters are software components that provide the ability to extract text from a particular file format. They were originally conceived so the Microsoft Indexing Service could be extended to non-MS file formats, but they can now used by many search programs including {ProductName} and some personal desktop search programs. Generally, one IFilter will handle one file format, but some handle multiple. Bear in mind that IFilters will only ever extract plain text, so you won't get any formatting (headings, bold, italics, etc) in their output.

WHERE TO GET THEM

Some software producers provide them for their own file formats, but there are specialist IFilter developers who have a range of them. Here’s three very useful links:

• http://www.ifilter.org - Description, FAQ, links to free IFilters.
• http://www.ifiltershop.com - Wide range of IFilters, including 'free for non-commercial' versions. They do Server editions and Workstation editions - I have only tested their Workstation versions, and found they work fine with {ProductName}.
• http://www.citeknet.com - Some IFilters, plus the very useful (and free) IFilter Explorer which lists the installed IFilters on your system. (Use the 'Indexing Services 3.0' tab within it to check which IFilter is used for each extension.)

HOW TO USE THEM WITH {ProductName}

First, download and install the required IFilter. This registers it with the operating system. You then need to add a line to your index configuration file to specify that {ProductName} should use the associated IFilter for a particular file extension. There are two ways to do this:

Method #1 (The hard core way!)

• Close Perceptive Enterprise Search - Local Administration Console
• Open the index's ISYS.CFG file in Notepad
• At the bottom of the file are the file rules, here's an example -

  Code:
  Under H:
  AUTO        MYFOLDER\DOCS\**\*.*

• Add a line below the 'Under' line (and above the other file rules) to specify that the installed IFilter should be used for a specified extension (.WMV in this example), so that it looks like this -

  Code:
  Under H:
  IFILTER    MYFOLDER\DOCS\**\*.WMV
  AUTO        MYFOLDER\DOCS\**\*.*

• Save the file
• Open Perceptive Enterprise Search - Local Administration Console and run the indexing. (In this example, WMVs would not have been indexed before, so you could just run an Update, but if you're changing how a file extension is being handled you'd need to reindex.)

Method #2 (The GUI way)

• In Perceptive Enterprise Search - Local Administration Console, open the relevant index.
• Click on Index > Content Sources
• Click on File Rules
• Click the blank page toolbar button 'Create a new file indexing rule'
• Navigate to the top level folder that contains the type of file you want to index with the IFilter
• Click on one example of that file type to select it, then click Next
• Check that the scope says 'Include - all *.ext files in and under <location>' (where .ext is the extension and <location> is the folder)
• Click the Advanced button
• In the 'Edit the final indexing rule' field change AUTO to IFILTER
• Click Finish
• Run the indexing. (If the file type has not been indexed before, you could just run an Update, but if you're changing how a file extension is being handled you'd need to reindex.)

Some IFilters do unexpected things that may be of benefit to some users. For example, the IFilterShop MSG IFilter extracts the text from attachments and appends it to the body of the email, so that the message and all attachments is taken as one document within {ProductName}.