xref: /freebsd/usr.bin/tsort/tsort.1 (revision 9b50d9027575220cb6dd09b3e62f03f511e908b8)
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35.\"     @(#)tsort.1	8.3 (Berkeley) 4/1/94
36.\"
37.Dd April 1, 1994
38.Dt TSORT 1
39.Os
40.Sh NAME
41.Nm tsort
42.Nd topological sort of a directed graph
43.Sh SYNOPSIS
44.Nm tsort
45.Op Fl l
46.Op Ar file
47.Sh DESCRIPTION
48.Nm Tsort
49takes a list of pairs of node names representing directed arcs in
50a graph and prints the nodes in topological order on standard output.
51Input is taken from the named
52.Ar file ,
53or from standard input if no file
54is given.
55.Pp
56Node names in the input are separated by white space and there must
57be an even number of node pairs.
58.Pp
59Presence of a node in a graph can be represented by an arc from the node
60to itself.
61This is useful when a node is not connected to any other nodes.
62.Pp
63If the graph contains a cycle (and therefore cannot be properly sorted),
64one of the arcs in the cycle is ignored and the sort continues.
65Cycles are reported on standard error.
66.Pp
67The options are as follows:
68.Bl -tag -width Ds
69.It Fl l
70Search for and display the longest cycle.
71Can take a very long time.
72.El
73.Sh SEE ALSO
74.Xr ar 1
75.Sh HISTORY
76A
77.Nm
78command appeared in
79.At v7 .
80This
81.Nm tsort
82command and manual page are derived from sources contributed to Berkeley by
83Michael Rendell of Memorial University of Newfoundland.
84