How to use the command tsort (with examples)

The tsort command is used to perform a topological sort on a directed acyclic graph. It can be used to show the dependency order of nodes in the graph. This command is helpful when there are dependencies between different elements, and you want to determine the order in which they should be processed or executed.

Use case 1: Perform a topological sort consistent with a partial sort per line of input separated by blanks

Code:

tsort path/to/file

Motivation:

This use case is helpful when you have a file containing a list of nodes or elements, and each line represents a partial sort order. By using tsort with the path to the file as an argument, you can determine the complete topological sort order consistent with the partial sort specified in the file.

Explanation:

• tsort: The command itself performs the topological sort.
• path/to/file: The path to the file containing the list of nodes or elements and their partial sort order. Each line in the file represents a partial sort order.

Example output:

Suppose we have a file nodes.txt with the following contents:

Backend
Database
UI

Running the command tsort nodes.txt will produce the following output:

Backend
Database
UI

This output indicates that the topological sort order consistent with the specified partial sort in the file is “Backend” -> “Database” -> “UI”.

Use case 2: Perform a topological sort consistent on strings.

Code:

echo -e "UI Backend\nBackend Database\nDocs UI" | tsort

Motivation:

This use case is useful when you want to perform a topological sort on a set of strings directly without using a file. By using the echo command to provide the input strings and piping it to tsort, you can perform the required topological sort.

Explanation:

• echo -e "UI Backend\nBackend Database\nDocs UI": This command prints the input strings separated by newline characters using the -e option of echo.
• |: The pipe symbol is used to redirect the output of echo to the input of tsort.
• tsort: The command performs the topological sort.

Example output:

Running the command echo -e "UI Backend\nBackend Database\nDocs UI" | tsort will produce the following output:

Backend
Database
Docs
UI

The output indicates the topological sort order of the input strings is “Backend” -> “Database” -> “Docs” -> “UI”.

Conclusion:

The tsort command is a versatile tool for performing topological sorting, which is useful for determining the dependency order of nodes in a directed acyclic graph. It can be used with both file input and direct string input, making it flexible in different scenarios.