NAME

       acyclic - make directed graph acyclic

SYNOPSIS

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

DESCRIPTION

       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
       input graph is stored; by default, the program reads from stdin.

OPTIONS

       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.

RETURN CODES

       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.

BUGS

       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.

AUTHORS

       Stephen C. North <north@research.att.com>
       Emden R. Gansner <erg@research.att.com>

SEE ALSO

       gc(1), dot(1), gvpr(1), gvcolor(1), ccomps(1), sccmap(1), tred(1), libgraph(3)

                                          21 March 2001                                ACYCLIC(1)