Repository navigation
tty.isatty(1) and process.stdout.isTTY in worker_threads worker return different values #28386
Description
Activity
See #26946 (comment)
Thanks for the link, interesting. But it doesn't say anything about
tty.isattyAPI, does it?You're welcome to open a documentation pull request but where would you add it? There are tens if not hundreds of core methods that accept a file descriptor. It'd be incongruent to single out
tty.isatty().Its behavior also isn't the least bit surprising to me but maybe that's just me.
Reacted by Anna Henningsen and snekFor me as a Node.JS developer, it's not clear if I should use
tty.isatty(fd)orprocess.stdout.isTTY- they look the same from the documentation and also the documentation doesn't explicitly say that one is about the process even when we create a thread within this process and another is talking about a thread.I’m having the same issue as Ben here – I don’t see a good place in the documentation that isn’t “everywhere”…
For me as a Node.JS developer, it's not clear if I should use
tty.isatty(fd)orprocess.stdout.isTTYWe could document that
tty.isatty(fd)should be used when dealing with a file descriptor, andprocess.stdout.isTTYwhen dealing withprocess.stdout, but that seems somewhat redundant? But that’s kind of the answer to the question of which function to use…Exactly.
I would think of the fd-handling functions as low-level primitives that are there for when you really need them, but generally dealing with the corresponding JS objects makes more sense when available (e.g. 99 % of the time using
fs.createReadStream()makes more sense then manually reading data usingfs.read()).In the case of
isatty(), I think the use cases are very limited. I could see somebody using it for detecting TTY-ness for non-stdio fd’s (e.g. for nativeopenpty()ortcgetattr()/tcsetattr()wrappers), or maybe when the goal is to intentionally test the per-process state, including whenprocess.stdouthas been overridden or when you’re in a Worker. But here too, I think 99 % of the time you’d want to use the convenience JS objects.Is that helpful? Is that something that we could or should document in some way?
it's also worth noting that accessing process.std{out, in, err} can change their modes and that node will start processing data (which may or may not be a good thing depending on your use case)
Related to this, we may want to properly publicly (think, docs) expose
process.stdout.fd?- added 2 commits that reference this issue
on Jan 10, 2020 - added 2 commits that reference this issue
on Mar 14, 2020 - added a commit that references this issue
on Jul 27, 2026
I found out recently that in a worker which is run with
worker_threads,tty.isatty(1)returns True whereasprocess.stdout.isTTYreturns False.This led to a weird issue in
mocha- a popular library for testing: mochajs/mocha#3955