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       acyclic - make directed graph acyclic


       acyclic [ -nv?  ] [ -o outfile ] [ file ]


       acyclic  is a filter that takes a directed graph as input and outputs a
       copy of the graph with sufficient edges  reversed  to  make  the  graph
       acyclic.  The  reversed  edge  inherits  all  of  the attributes of the
       original edge. The optional file argument specifies where the the input
       graph is stored; by default, the program reads from stdin.


       The following options are supported:

       -n     No  output  is  produced,  though the return value will indicate
              whether the graph is acyclic or not.

       -v     Print information about whether the file is acyclic, has a cycle
              or is undirected.

       -o outfile
              causes  the  output  to  be  written  to  the specified file; by
              default, output is written to stdout.

       -?     option causes the program to print usage information.


       acyclic returns 0 if the graph is acyclic; 1 if the graph has a  cycle;
       2 if the graph is undirected; and 255 if there are any errors.


       If the graph is strict and there is a cycle of length 2, the attributes
       of the reversed edge are lost.

       Some edge attributes are non-symmetric, referring to either the head or
       tail  node.  At  present,  there  is  no  mechanism  or  convention for
       correctly switching or renaming these.


       Stephen C. North <>
       Emden R. Gansner <>


       gc(1), dot(1),  gvpr(1),  gvcolor(1),  ccomps(1),  sccmap(1),  tred(1),

                                 21 March 2001