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       dijkstra - single-source distance filter


       dijkstra [ -ap?  ] [ sourcenode file ]


       dijkstra reads a stream of graphs and for each computes the distance of
       every node from sourcenode.  Edge length is given in the len attribute,
       and  the  default is 1.  The dist attribute of every node is set to its
       distance from sourcenode.  If the -p flag is used, the  prev  attribute
       of  each  node  reachable  from  sourcenode  is  set to the name of the
       previous node on a shortest path.  The graph attribute maxdist  is  set
       to the maximum dist of all nodes in the graph.

       By  default,  if the graph is disconnected, the dist attribute of nodes
       unreachable from sourcenode are left untouched, and maxdist is  set  to
       the  maximum of any previous value and the largest distance recorded in
       this run. On the other hand, if the -a flag is used, the dist attribute
       of  an  unreachable  node  is  assigned a very large value, and maxdist
       records  the  maximum  distance  found  in  the  component   containing

       Any  number of sourcenode file pairs may be given.  If the last file is
       missing, stdin is used.  All output is written to stdout.

       In a typical application, dist  and  maxdist  can  drive  a  downstream
       calculation of color or some other attribute.


       gvpr(1), gvcolor(1), libgraph(3)

                                 21 March 2001