If the .dot file is saved as test1.dot and the following script is run:

tclsh test1.tcl test1.dot a0 b3Then the colored.dot file will display the shortest path between a0 and b3 in red.The example dosn't specify any weights for the edges, a default weight of 1 will be assigned to each edge. In order to assign other weights to an edge add an attribute of weight to the edge like this:

n1 -> n2[weight="5"]

**Sample test1.dot file ----------------------------**digraph G {

a0 -> a1 -> a2 -> a3; b0 -> b1 -> b2 -> b3; x -> a0; x -> b0; a1 -> b3; b1 -> a3;}

**test1.tcl code start ---------------------------**

# Test script 1 for the DGA package. Test the shortest path implementation # in the DGA package. package require ASDOT package require DGA # This script takes three input parameters. # graphName - The .dot file that is to be loaded # startNode - The node to be used for the start of the shortest # path calculation. The algorithm finds the shortest # path to all other reachable nodes from this starting node # endNode - The node to display the shortest path to. set graphName [lindex $argv 0] set startNode [lindex $argv 1] set endNode [lindex $argv 2] # Read the .dot file in and build the TCL graph from it set graph [ASDOT::read_dot $graphName] # Calculate the shortest path to all reachanble nodes from the # startNode DGA::shortest_path $graph $startNode # Get back the predecesor list. For each node n this defines # it's predecessor (if any) that will route back to the startNode set pl [DGA::predecessor_list $graph] puts $pl # Now colour the graph to show the route from the endNode to the # startNode set cn $endNode while {1} { $graph node set $cn -key color red set arc [$graph node get $cn -key predecessor] if { $arc == {} } {break} $graph arc set $arc -key color red set cn [$graph arc source $arc] if { $cn == $startNode } { $graph node set $startNode -key color red break ; } } # Write out the graph to colored.dot, when displayed using dotty this # should show the shortest path from startNode to endNode in red ASDOT::write_dot colored.dot $graph # Display the shortest path nodes and arcs using the pl_ helper # functions set pNode [DGA::pl_node $pl $endNode] set pArc [DGA::pl_arc $pl $endNode] set pDist [DGA::pl_dist $pl $endNode] puts "$endNode $pDist $pArc" while {1} { set pDist [DGA::pl_dist $pl $pNode] set pArc [DGA::pl_arc $pl $pNode] puts "$pNode $pDist $pArc" set pNode [DGA::pl_node $pl $pNode] if { $pNode == {} } { break } } # Tidy up the graph $graph destroy