TSORT(1)                   OpenBSD Reference Manual                   TSORT(1)

NAME
     tsort - topological sort of a directed graph



SYNOPSIS
     tsort [-l] [-q] [file]

DESCRIPTION
     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.  In-
     put is taken from the named file, or from standard input if no file is
     given.

     Node names in the input are separated by white space and there must be an
     even number of node pairs.

     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.

     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.

     The options are as follows:

     -l      Search for and display the longest cycle.  Can take a very long
             time.

     -q      Do not display informational messages about cycles.  This is pri-
             marily intended for building libraries, where optimal ordering is
             not critical, and cycles occur often.

SEE ALSO
     ar(1)

HISTORY
     A tsort command appeared in Version 7 AT&T UNIX.  This tsort command and
     manual page are derived from sources contributed to Berkeley by Michael
     Rendell of Memorial University of Newfoundland.

OpenBSD 2.6                      April 1, 1994                               1