$ProcessID
gives the ID assigned to the Wolfram Language kernel process by the operating system under which it is run.
Examples
Basic Examples (1)
Wolfram Research (1996), $ProcessID, Wolfram Language function, https://reference.wolfram.com/language/ref/$ProcessID.html.
Text
Wolfram Research (1996), $ProcessID, Wolfram Language function, https://reference.wolfram.com/language/ref/$ProcessID.html.
CMS
Wolfram Language. 1996. "$ProcessID." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/$ProcessID.html.
APA
Wolfram Language. (1996). $ProcessID. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/$ProcessID.html