tsort.1

早期freebsd实现

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.\"     @(#)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 Ar file
.Sh DESCRIPTION
.Nm Tsort
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 white space 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.
.El
.Sh SEE ALSO
.Xr ar 1
.Sh HISTORY
A
.Nm
command appeared in
.At v7 .
This
.Nm tsort
command and manual page are derived from sources contributed to Berkeley by
Michael Rendell of Memorial University of Newfoundland.