Annotation of src/usr.bin/tsort/tsort.1, Revision 1.16
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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
1.16 ! espie 44: .Op Fl flqrvw
1.7 espie 45: .Op Fl h Ar file
1.1 deraadt 46: .Op Ar file
47: .Sh DESCRIPTION
1.7 espie 48: .Nm tsort
1.1 deraadt 49: takes a list of pairs of node names representing directed arcs in
50: a graph and prints the nodes in topological order on standard output.
1.16 ! espie 51: That is, the input describes a partial ordering relation, from which
1.15 espie 52: .Nm
53: computes a total order compatible with this partial ordering.
54: .Pp
1.1 deraadt 55: Input is taken from the named
56: .Ar file ,
57: or from standard input if no file
58: is given.
59: .Pp
1.7 espie 60: Node names in the input are separated by white space and there must
1.1 deraadt 61: be an even number of node pairs.
62: .Pp
63: Presence of a node in a graph can be represented by an arc from the node
64: to itself.
65: This is useful when a node is not connected to any other nodes.
66: .Pp
67: If the graph contains a cycle (and therefore cannot be properly sorted),
68: one of the arcs in the cycle is ignored and the sort continues.
69: Cycles are reported on standard error.
70: .Pp
71: The options are as follows:
72: .Bl -tag -width Ds
1.7 espie 73: .It Fl f
1.12 millert 74: Resolve ambiguities by selecting nodes based on the order of appearance
1.7 espie 75: of the first component of the pairs.
76: .It Fl h Ar file
77: Use
78: .Ar file ,
79: which holds an ordered list of nodes, to resolve ambiguities.
1.8 espie 80: In case of duplicates, the first entry is chosen.
1.2 deraadt 81: .It Fl l
1.1 deraadt 82: Search for and display the longest cycle.
1.10 espie 83: Can take a very long time, as it may need to solve an NP-complete problem.
1.2 deraadt 84: .It Fl q
1.14 jmc 85: Do not display informational messages about cycles.
86: This is primarily intended for building libraries, where optimal ordering
1.8 espie 87: is not critical, and cycles occur often.
1.7 espie 88: .It Fl r
89: Reverse the ordering relation.
90: .It Fl v
91: Inform on the exact number of edges broken while breaking cycles.
1.8 espie 92: If a hints file was used, inform on seen nodes absent from that file.
1.7 espie 93: .It Fl w
94: Exit with exit code the number of cycles
95: .Nm
96: had to break.
1.1 deraadt 97: .El
1.15 espie 98: .Sh EXAMPLES
99: Faced with the input:
1.16 ! espie 100: .Bd -literal -offset indent
1.15 espie 101: a b
102: b c
103: b d
104: d f
105: c e
106: .Ed
107: .Pp
108: .Nm
109: outputs:
1.16 ! espie 110: .Bd -literal -offset indent
1.15 espie 111: a
112: b
113: c
114: e
115: d
116: f
117: .Ed
118: .Pp
119: which is one total ordering compatible with the individual relations.
120: There is no unicity, another compatible total ordering would be:
1.16 ! espie 121: .Bd -literal -offset indent
1.15 espie 122: a
123: b
124: c
125: d
126: e
127: f
128: .Ed
129: .Pp
130: .Nm
131: is commonly used to analyze dependencies and find a correct build order
132: in a static way, whereas
133: .Xr make 1
134: accomplishes the same task in a dynamic way.
1.1 deraadt 135: .Sh SEE ALSO
1.7 espie 136: .Xr ar 1 ,
1.15 espie 137: .Xr lorder 1 ,
138: .Xr make 1
1.7 espie 139: .Rs
140: .%A Donald E. Knuth
141: .%B The Art of Computer Programming
142: .%V Vol. 1
143: .%P pp 258-268
144: .%D 1973
145: .Re
1.1 deraadt 146: .Sh HISTORY
147: A
148: .Nm
149: command appeared in
150: .At v7 .
151: This
1.7 espie 152: .Nm tsort
153: command was completely rewritten by Marc Espie for
154: .Ox ,
155: to finally use the well-known optimal algorithms for topological sorting.