$Urgent
gives the list of files and pipes to which urgent output from the Wolfram Language is sent.
Examples
Wolfram Research (1988), $Urgent, Wolfram Language function, https://reference.wolfram.com/language/ref/$Urgent.html.
Text
Wolfram Research (1988), $Urgent, Wolfram Language function, https://reference.wolfram.com/language/ref/$Urgent.html.
CMS
Wolfram Language. 1988. "$Urgent." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/$Urgent.html.
APA
Wolfram Language. (1988). $Urgent. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/$Urgent.html