tsort

tsort is a command line tool used for topological sorting in Unix-like operating systems. It stands for "topological sort" and is used to sort a directed acyclic graph (DAG). The goal of topological sorting is to arrange the nodes in such a way that for every directed edge (u, v), node u comes before node v in the sorted order.

1. tsort reads a text file containing a DAG as input.
2. The input file defines the nodes and their dependencies.
3. Each line consists of two node names separated by a whitespace, representing a directed edge from the first node to the second.
4. tsort outputs a linear ordering of the nodes, such that for every edge (u, v), u comes before v in the output.
5. If the input graph has cycles, tsort detects them and reports an error.
6. It uses a depth-first search algorithm to perform the topological sorting.
7. In case of multiple valid orderings, tsort outputs any valid ordering.
8. The sorted output is printed to the standard output.
9. If there are no input files provided, tsort reads from the standard input.
10. tsort is commonly used for dependency resolution, build systems, and task scheduling.