UML diagram for print command using singleton pattern

Maybe you can find an UML tool to your liking here: https://www.slant.co/topics/4978/~what-is-the-fastest-way-to-create-and-edit-uml-diagrams[^]
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<img src='https://g.gravizo.com/svg?
digraph G {
main -> parse -> execute;
main -> init;
main -> cleanup;
execute -> make_string;
execute -> printf
init -> make_string;
main -> printf;
execute -> compare;
}
'/>

Example diagram[^]