TSORT(1) | 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.
There must be an even number of nodes in the input. Node names specified on the same line should be white space separated.
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:
Assuming a file named dag with the following contents representing a directed acyclic graph:
A B A F B C B D D E
Sort the nodes of the graph:
$ tsort dag A F B D C E
White spaces and new line characters are considered equal. This file for example is considered equal to the one we defined before:
$ cat dga A B A F B C B D D E
Assume we add a new directed arc from D to A creating a cycle:
A B A F B C B D D E D A
Ordering the graph detects the cycle:
$ tsort dag tsort: cycle in data tsort: A tsort: B tsort: D D E A F B C
Same as above but silencing the warning about the cycle:
$ tsort -q dag D E A F B C
The 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.
August 30, 2020 | macOS 14.6 |