File Attachments

Each topic can have one or more files of any type attached to it by using the Attach screen to upload (or download) files from your local PC. Attachments are stored under revision control: uploads are automatically backed up; all previous versions of a modified file can be retrieved.

What Are Attachments Good For?

File Attachments can be used to create powerful customized groupware solutions, like file sharing and document management systems, and quick Web page authoring.

Document Management System

• You can use Attachments to store and retrieve documents (in any format, with associated graphics, and other media files); attach documents to specific TWiki topics; collaborate on documents with full revision control; distribute documents on a need-to-know basis using web and topic-level access control; create a central reference library that's easy to share with an user group spread around the world.

File Sharing

• For file sharing, FileAttachments on a series of topics can be used to quickly create a well-documented, categorized digital download center for all types of files: documents; graphics and other media; drivers and patches; applications; anything you can safely upload!

Web Authoring

• Through your Web browser, you can easily upload graphics (or sound files, or anything else you want to link to on a page) and place them on a single page, or use them across a web, or site-wide.
  • NOTE: You can also add graphics - any files - directly, typically by FTP upload. This requires FTP access, and may be more convenient if you have a large number of files to load. FTP-ed files can't be managed using browser-based Attachment controls. You can use your browser to create TWikiVariables shortcuts, like this %H% = .

Uploading Files

• Click on the Attach link at the bottom of the page. The Attach screen lets you browse for a file, add a comment, and upload it. The uploaded file will show up in the File Attachment table.
  • Any type of file can be uploaded. Some files that might pose a security risk are renamed, ex: *.php files are renamed to *.php.txt so that no one can place code that would be read in a .php file.
  • The previous upload path is retained for convenience. In case you make some changes to the local file and want to upload it, again you can copy the previous upload path into the Local file field.
  • TWiki can limit the file size. This is defined by the %ATTACHFILESIZELIMIT% variable of the TWikiPreferences, currently set at 10000 KB.
    • It's not recommended to upload files greater than a few hundred K through a browser. Large files can be extremely slow-loading, and often time out. Use an FTP site for large file uploads.

Downloading Files

• Click on the file in the File Attachment table.

• NOTE: There is no access control on individual attachments. If you need control over single files, create a separate topic per file and set topic-level access restrictions for each.

Moving Attachment Files

An attachment can be moved between topics.

• Click Action on the Attachment to be moved.
• On the control screen, select the new web and/or topic.
• Click Move. The attachment and its version history are moved. The original location is stored as topic Meta Data.

Deleting Attachments

It is not possible to delete attached files directly. You can delete a topic, and its attachments with it.

• One easy workaround is to create a Trash.TrashAttachments - then, simply move unwanted Attachments to that topic.

Linking to Attached Files

• Once a file is attached it can be referenced in the topic. Example:
  1. Attach file: Sample.txt
  2. Edit topic and enter: %ATTACHURL%/Sample.txt
  3. Preview: %ATTACHURL%/Sample.txt text appears as: https://moglen.law.columbia.edu/twiki/pub/TWiki/FileAttachment/Sample.txt, a link to the text file.

• To reference an attachment located in another topic, enter:
  • %PUBURL%/%WEB%/OtherTopic/Sample.txt (if it's within the same web)
  • %PUBURL%/Otherweb/OtherTopic/Sample.txt (if it's in a different web)

• Attached HTML files and text files can be inlined in a topic. Example:
  1. Attach file: Sample.txt
  2. Edit topic and write text: %INCLUDE{"%ATTACHURL%/Sample.txt"}%
     • Content of attached file is shown inlined.
     • Read more in IncludeTopicsAndWebPages.

• GIF, JPG and PNG images can be attached and shown embedded in a topic. Example:
  1. Attach file: Smile.gif
  2. Edit topic and write text: %ATTACHURL%/Smile.gif
  3. Preview: text appears as , an image.

File Attachment Contents Table

Files attached to a topic are displayed in a directory table, displayed at the bottom of the page, or optionally, hidden and accessed when you click Attach.

Attachment: Action: Size: Date: Who: Comment: Sample.txt action 30 22 Jul 2000 - 19:37 PeterThoeny Just a sample Smile.gif action 94 22 Jul 2000 - 19:38 PeterThoeny Smiley face

File Attachment Controls

Clicking on an Action link takes you to a new page that looks like this:

Attachment: Action: Size: Date: Who: Comment: Attribute: Sample.txt action 30 22 Jul 2000 - 19:37 PeterThoeny Just a sample   Smile.gif action 94 22 Jul 2000 - 19:38 PeterThoeny Smiley face   Update attachment Sample.txt Version: Action: Date: Who: Comment: 1.1 view 2001.08.30.09.28.56 PeterThoeny   Previous upload: C:\DATA\Sample.txt (PeterThoeny) Local file: Comment: Link: Create a link to the attached file at the end of the topic. Hide file: Hide attachment in normal topic view. Help text ... Topic FileAttachment . { | | Move attachment | Cancel }

• The first table is a list of all attachments, including their attributes. An h means the attachment is hidden, it isn't listed when viewing a topic.

• The second table is all the versions of the attachment. Click on View to see that version. If it's the most recent version, you'll be taken to an URL that always displays the latest version, which is usually what you want.
  • To change the comment on an attachment, enter a new comment and then click Change properties. Note that the comment listed against the specific version will not change, however the comment displayed when viewing the topic does change.
  • To hide/unhide an attachment, enable the Hide file checkbox, then click Change properties.

Known Issues

• Unlike topics, attachments are not locked during editing. As a workaround, you can change the comment to indicate an attachment file is being worked on - the comment on the specific version isn't lost, it's there when you list all versions of the attachment.