The tsort command is a utility that performs topological sorting of a directed acyclic graph (DAG). Topological sorting is an algorithm that orders the vertices of a DAG such that for every directed edge u -> v, u comes before v in the order.
To use the tsort command, you can type tsort followed by the input file that contains the graph. The input file should contain one edge per line, with the edges in the form u v, where u is the source vertex and v is the destination vertex.
For example, to perform topological sorting of the graph represented by the file graph.txt, you can use the following command:
tsort graph.txt
This will perform topological sorting of the graph and display the sorted vertices on the standard output.
If the graph contains a cycle, tsort will display an error message and exit with a non-zero exit status.
To save the sorted vertices to a file, you can redirect the output of tsort to a file. For example:
tsort graph.txt > sorted.txt
This will perform topological sorting of the graph and save the sorted vertices to the sorted.txt file.
It is important to note that the tsort command expects the input file to be in a specific format, and may not handle input that does not conform to this format correctly.
For more information about the tsort command and its usage, you can consult the documentation for your specific Unix or Linux system.