|TSORT(1)||General Commands Manual||TSORT(1)|
tsorttakes a list of pairs of node names representing directed arcs in a graph and prints the nodes in topological order on standard output. That is, the input describes a partial ordering relation, from which
tsortcomputes a total order compatible with this partial ordering.
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 node names.
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:
tsorthad to break.
tsortutility exits 0 on success, and >0 if an error occurs.
a b b c b d d f c e
a b c e d f
which is one total ordering compatible with the individual relations. There is no unicity, another compatible total ordering would be:
a b c d e f
tsort is commonly used to analyze
dependencies and find a correct build order in a static way, whereas
make(1) accomplishes the same task in a
Donald E. Knuth, The Art of Computer Programming, Vol. 1, pp 258-268, 1973.
tsortutility is compliant with the IEEE Std 1003.1-2008 (“POSIX.1”) specification.
The flags [
-fhlqrvw] are extensions to
tsortcommand appeared in Version 7 AT&T UNIX. This
tsortcommand was completely rewritten by Marc Espie for OpenBSD, to finally use the well-known optimal algorithms for topological sorting.
|March 29, 2012||OpenBSD-current|