Webdot doesn't work.

We assume you're using Apache and have TCL installed. If you don't, it's probably better to just use the webdot perl script.

To debug webdot, first test whether tclsh can load the Tcldot shared library. Try:

  • $ tclsh
    % load $prefix/lib/graphviz/tcl/libtcldot.so.0

where $prefix is the installation prefix for graphviz; usually /usr or /usr/local.

Then test whether webdot runs from a shell command. (With webdot we provide a helper script scaffold.tcl or scaffold.sh that sets up an environment like the one Apache provides.) For example

  • $ scaffold.tcl >out.gif
    can't read "LIBTCLDOT": no such variable

    • while executing

    "file mtime $LIBTCLDOT"

    • invoked from within

    "set t1 [file mtime $LIBTCLDOT]"

    • (file "cgi-bin/webdot" line 67)
      invoked from within

    "source cgi-bin/webdot

    • (file "scaffold.tcl" line 22)

The above is a strong clue that webdot is not configured properly.

Finally, test whether webdot runs as a cgi-bin program. It may help to examine the cgi-bin environment using a simple cgi-bin tcl script like:

  • #!/bin/env tclsh
    puts "Content-type: text/plain"
    puts ""
    foreach e [lsort [array names env]] {puts "$e: $env($e)"}

Save this script as .../cgi-bin/test.tcl, make it executable, then look at: http://localhost/cgi-bin/test.tcl

Also, if you see something like:

  • WebDot Error:
    Response Code = 403

This usually means that webdot ran succesfully, but was not able to fetch the remote graph from the URL you gave as an argument. The reason is probably that your server is behind a firewall that blocks the webdot server, so it cannot get the graph file. You can either change firewall permissions, put the graph on a different server, or install webdot locally so you don't need a remote server to fetch your graph data.

It would be nice if someone hacked webdot to take the contents of a graph as a cgi-bin argument, so it wouldn't need permission to fetch a graph remotely. This is left as an exercise for the Open Source Community.

GraphvizWiki: FaqWebdot (last edited 2008-01-17 18:30:57 by H-135-207-131-158)

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