prune - Prune directed graphs


prune [ -n node ] [ -N attrspec ] [ files ... ]


prune reads directed graphs in the same format used by dot(1) and removes subgraphs rooted at nodes specified on the command line via options. These nodes themselves will not be removed, but can be given attributes so that they can be easily located by a graph stream editor such as gpr(1). prune correctly handles cycles, loops and multi-edges.

Both options can appear multiple times on the command line. All subgraphs rooted at the respective nodes given will then be processed. If a node does not exist, prune will skip it and print a warning message to stderr. If multiple attributes are given, they will be applied to all nodes that have been processed. prune writes the result to the stdout.


-n name Specifies name of node to prune.
-N attrspec
 Specifies attribute that will be set (or changed if it exists) for any pruned node. attrspec is a string of the form attr=value.


An input graph of the form

        digraph DG {          A -> B;          A -> C;

         B -> D;          B -> E;         }

, processed by the command

        prune -n B

would produce the following output (the actual code might be formatted in a slightly different way).

        digraph DG {          A -> B;          A -> C;         }

Another input graph of the form

        digraph DG {          A -> B;          A -> C;

         B -> D;          B -> E;

         C -> E;         }

(note the additional edge from C to E ), processed by the command

        prune -n B -N color=red

results in

        digraph DG {          B [color=red];          A -> B;          A -> C;          C -> E;         }

Node E has not been removed since its second parent C is not being pruned.


prune returns 0 on successful completion. It returns 1 if an error occurs.


dot(1), gpr(1)


Marcus Harnisch <>

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