Annotation of src/usr.bin/tsort/tsort.1, Revision 1.15
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34: .\" @(#)tsort.1 8.3 (Berkeley) 4/1/94
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1.7 espie 36: .Dd November 1, 1999
1.1 deraadt 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
1.7 espie 44: .Op Fl f
45: .Op Fl h Ar file
1.1 deraadt 46: .Op Fl l
1.2 deraadt 47: .Op Fl q
1.7 espie 48: .Op Fl r
1.9 pvalchev 49: .Op Fl v
1.7 espie 50: .Op Fl w
1.1 deraadt 51: .Op Ar file
52: .Sh DESCRIPTION
1.7 espie 53: .Nm tsort
1.1 deraadt 54: takes a list of pairs of node names representing directed arcs in
55: a graph and prints the nodes in topological order on standard output.
1.15 ! espie 56: That is: the input describes a partial ordering relation, from which
! 57: .Nm
! 58: computes a total order compatible with this partial ordering.
! 59: .Pp
1.1 deraadt 60: Input is taken from the named
61: .Ar file ,
62: or from standard input if no file
63: is given.
64: .Pp
1.7 espie 65: Node names in the input are separated by white space and there must
1.1 deraadt 66: be an even number of node pairs.
67: .Pp
68: Presence of a node in a graph can be represented by an arc from the node
69: to itself.
70: This is useful when a node is not connected to any other nodes.
71: .Pp
72: If the graph contains a cycle (and therefore cannot be properly sorted),
73: one of the arcs in the cycle is ignored and the sort continues.
74: Cycles are reported on standard error.
75: .Pp
76: The options are as follows:
77: .Bl -tag -width Ds
1.7 espie 78: .It Fl f
1.12 millert 79: Resolve ambiguities by selecting nodes based on the order of appearance
1.7 espie 80: of the first component of the pairs.
81: .It Fl h Ar file
82: Use
83: .Ar file ,
84: which holds an ordered list of nodes, to resolve ambiguities.
1.8 espie 85: In case of duplicates, the first entry is chosen.
1.2 deraadt 86: .It Fl l
1.1 deraadt 87: Search for and display the longest cycle.
1.10 espie 88: Can take a very long time, as it may need to solve an NP-complete problem.
1.2 deraadt 89: .It Fl q
1.14 jmc 90: Do not display informational messages about cycles.
91: This is primarily intended for building libraries, where optimal ordering
1.8 espie 92: is not critical, and cycles occur often.
1.7 espie 93: .It Fl r
94: Reverse the ordering relation.
95: .It Fl v
96: Inform on the exact number of edges broken while breaking cycles.
1.8 espie 97: If a hints file was used, inform on seen nodes absent from that file.
1.7 espie 98: .It Fl w
99: Exit with exit code the number of cycles
100: .Nm
101: had to break.
1.1 deraadt 102: .El
1.15 ! espie 103: .Sh EXAMPLES
! 104: Faced with the input:
! 105: .Bd -literal
! 106: a b
! 107: b c
! 108: b d
! 109: d f
! 110: c e
! 111: .Ed
! 112: .Pp
! 113: .Nm
! 114: outputs:
! 115: .Bd -literal
! 116: a
! 117: b
! 118: c
! 119: e
! 120: d
! 121: f
! 122: .Ed
! 123: .Pp
! 124: which is one total ordering compatible with the individual relations.
! 125: There is no unicity, another compatible total ordering would be:
! 126: .Bd -literal
! 127: a
! 128: b
! 129: c
! 130: d
! 131: e
! 132: f
! 133: .Ed
! 134: .Pp
! 135: .Nm
! 136: is commonly used to analyze dependencies and find a correct build order
! 137: in a static way, whereas
! 138: .Xr make 1
! 139: accomplishes the same task in a dynamic way.
1.1 deraadt 140: .Sh SEE ALSO
1.7 espie 141: .Xr ar 1 ,
1.15 ! espie 142: .Xr lorder 1 ,
! 143: .Xr make 1
1.7 espie 144: .Rs
145: .%A Donald E. Knuth
146: .%B The Art of Computer Programming
147: .%V Vol. 1
148: .%P pp 258-268
149: .%D 1973
150: .Re
1.1 deraadt 151: .Sh HISTORY
152: A
153: .Nm
154: command appeared in
155: .At v7 .
156: This
1.7 espie 157: .Nm tsort
158: command was completely rewritten by Marc Espie for
159: .Ox ,
160: to finally use the well-known optimal algorithms for topological sorting.
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