TSORT(1) MidnightBSD General Commands Manual TSORT(1)


tsort — topological sort of a directed graph


tsort [−dlq] [file]


The tsort utility 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 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 nodes.

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:


Turn on debugging.


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


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




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.


The tsort utility does not recognize multibyte characters.

MidnightBSD 0.3 July 3, 2004 MidnightBSD 0.3