Check output device is a terminal: Difference between revisions
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<lang js>node -p -e "Boolean(process.stdout.isTTY)"
true</lang>
=={{header|J}}==
<lang J>3=nc<'wd'</lang>
Explanation:
J does not have a concept of an "output device", so we approximate that by seeing whether we have bothered to define a the code which typically does graphical output.
The use of the phrase "output device" suggests that we are thinking about something like the unix `isatty` command. Here, stdout might be a file or might be a terminal. But in J we are often hosting our own user interaction environment. It's not uncommon for a J user to be on a web page where hitting enter sends a form request to a J interpreter which in turn composes an updated html presentation of current state which it sends to the browser. Or, the J user might be talking to a Java program which similarly wraps the J session (though this is older technology at this point). Or, the J user might be interacting with Qt. Or, sure, we might be talking to a tty and J might be sending its output straight to the tty. (But we can't know if that tty is hosted in emacs, running under control of a script on a remote machine via ssh, talking directly to a human user who happens to be in direct control of the session, or whatever else...)
The point being that in the general case the J programmer cannot know whether the concept of "terminal" has any relevance to the user.
But, like everyone else, we can certainly use heuristics.
But, correctness requires us to keep in mind that these will only be heuristics, and will sometimes be incorrect (hopefully not often enough to matter a lot...).
=={{header|Julia}}==
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