1.\" $OpenBSD: tsort.1,v 1.23 2012/03/29 22:04:28 jmc Exp $ 2.\" $NetBSD: tsort.1,v 1.6 1996/01/17 20:37:49 mycroft Exp $ 3.\" 4.\" Copyright (c) 1990, 1993, 1994 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" This manual is derived from one contributed to Berkeley by 8.\" Michael Rendell of Memorial University of Newfoundland. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)tsort.1 8.3 (Berkeley) 4/1/94 35.\" 36.Dd $Mdocdate: March 29 2012 $ 37.Dt TSORT 1 38.Os 39.Sh NAME 40.Nm tsort 41.Nd topological sort of a directed graph 42.Sh SYNOPSIS 43.Nm tsort 44.Op Fl flqrvw 45.Op Fl h Ar file 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. 51That is, the input describes a partial ordering relation, from which 52.Nm 53computes a total order compatible with this partial ordering. 54.Pp 55Input is taken from the named 56.Ar file , 57or from standard input if no file 58is given. 59.Pp 60Node names in the input are separated by white space and there must 61be an even number of node names. 62.Pp 63Presence of a node in a graph can be represented by an arc from the node 64to itself. 65This is useful when a node is not connected to any other nodes. 66.Pp 67If the graph contains a cycle (and therefore cannot be properly sorted), 68one of the arcs in the cycle is ignored and the sort continues. 69Cycles are reported on standard error. 70.Pp 71The options are as follows: 72.Bl -tag -width Ds 73.It Fl f 74Resolve ambiguities by selecting nodes based on the order of appearance 75of the first component of the pairs. 76.It Fl h Ar file 77Use 78.Ar file , 79which holds an ordered list of nodes, to resolve ambiguities. 80In case of duplicates, the first entry is chosen. 81.It Fl l 82Search for and display the longest cycle. 83Can take a very long time, as it may need to solve an NP-complete problem. 84.It Fl q 85Do not display informational messages about cycles. 86This is primarily intended for building libraries, where optimal ordering 87is not critical, and cycles occur often. 88.It Fl r 89Reverse the ordering relation. 90.It Fl v 91Inform on the exact number of edges broken while breaking cycles. 92If a hints file was used, inform on seen nodes absent from that file. 93.It Fl w 94Exit with exit code the number of cycles 95.Nm 96had to break. 97.El 98.Sh EXIT STATUS 99.Ex -std tsort 100.Sh EXAMPLES 101Faced with the input: 102.Bd -literal -offset indent 103a b 104b c 105b d 106d f 107c e 108.Ed 109.Pp 110.Nm 111outputs: 112.Bd -literal -offset indent 113a 114b 115c 116e 117d 118f 119.Ed 120.Pp 121which is one total ordering compatible with the individual relations. 122There is no unicity, another compatible total ordering would be: 123.Bd -literal -offset indent 124a 125b 126c 127d 128e 129f 130.Ed 131.Pp 132.Nm 133is commonly used to analyze dependencies and find a correct build order 134in a static way, whereas 135.Xr make 1 136accomplishes the same task in a dynamic way. 137.Sh SEE ALSO 138.Xr ar 1 , 139.Xr lorder 1 , 140.Xr make 1 141.Rs 142.%A Donald E. Knuth 143.%B The Art of Computer Programming 144.%V Vol. 1 145.%P pp 258-268 146.%D 1973 147.Re 148.Sh STANDARDS 149The 150.Nm 151utility is compliant with the 152.St -p1003.1-2008 153specification. 154.Pp 155The flags 156.Op Fl fhlqrvw 157are extensions to that specification. 158.Sh HISTORY 159A 160.Nm 161command appeared in 162.At v7 . 163This 164.Nm tsort 165command was completely rewritten by Marc Espie for 166.Ox , 167to finally use the well-known optimal algorithms for topological sorting. 168