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.\" $OpenBSD: tsort.1,v 1.6 2000/03/11 21:40:06 aaron Exp $
.\" $NetBSD: tsort.1,v 1.6 1996/01/17 20:37:49 mycroft Exp $
.\"
.\" Copyright (c) 1990, 1993, 1994
.\" The Regents of the University of California. All rights reserved.
.\"
.\" This manual is derived from one contributed to Berkeley by
.\" Michael Rendell of Memorial University of Newfoundland.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\" must display the following acknowledgement:
.\" This product includes software developed by the University of
.\" California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" @(#)tsort.1 8.3 (Berkeley) 4/1/94
.\"
.Dd April 1, 1994
.Dt TSORT 1
.Os
.Sh NAME
.Nm tsort
.Nd topological sort of a directed graph
.Sh SYNOPSIS
.Nm tsort
.Op Fl l
.Op Fl q
.Op Ar file
.Sh DESCRIPTION
.Nm
takes a list of pairs of node names representing directed arcs in
a graph and prints the nodes in topological order on standard output.
Input is taken from the named
.Ar file ,
or from standard input if no file
is given.
.Pp
Node names in the input are separated by whitespace and there must
be an even number of node pairs.
.Pp
Presence of a node in a graph can be represented by an arc from the node
to itself.
This is useful when a node is not connected to any other nodes.
.Pp
If the graph contains a cycle (and therefore cannot be properly sorted),
one of the arcs in the cycle is ignored and the sort continues.
Cycles are reported on standard error.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl l
Search for and display the longest cycle.
Can take a very long time.
.It Fl q
Do not display informational messages about cycles.
This is primarily
intended for building libraries, where optimal ordering is not critical,
and cycles occur often.
.El
.Sh SEE ALSO
.Xr ar 1
.Sh HISTORY
A
.Nm
command appeared in
.At v7 .
This
.Nm
command and manual page are derived from sources contributed to Berkeley by
Michael Rendell of Memorial University of Newfoundland.
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