is this a native thing that terminals provide or should one be synthesized from... something?

Honestly, I don't know what's the best way to go about this...

For Linux there's https://man7.org/linux/man-pages/man3/ttyname.3.html

In case it helps, this is what Jansi provides for Java through JNI and C: https://github.com/fusesource/jansi/tree/master/src/main/native

Can you write a proposed API with a doc comment? Thanks.

I'm currently very unfamiliar with the language, so apologies in advance if this is not what you are looking for, but looking at the current API, I think it would something like:

//GetName returns the name of the given terminal.
func GetName(fd int) string

If the given file descriptor is not a terminal, it could return empty or an error, according to what's considered best practice or following other similar cases in the package.

Then for example, assuming the current terminal is /dev/ttys001 and there is another terminal /dev/ttys002 and given a command my-command that prints to stdout the result of calling that method for stdin, stout and stderr, it would behave like this:

$my-command 2> /dev/ttys002
STDIN:  /dev/ttys001
STDOUT: /dev/ttys001
STDERR: /dev/ttys002

Go rarely uses file descriptors, so it seems odd to pass a file descriptor to a function like this. I mean, file descriptors do exist, of course, but Go programs don't use them routinely.

If the goal is only to check whether os.Stdout and os.Stderr are going to different files, then I don't think ttyname is the right approach at all. Instead, use the Stat method and compare the Dev and Ino fields of stat.Sys().(*syscall.Stat_t). Note that that is Unix-specific, but then so is ttyname.

You can also use os.SameFile, which basically does what @ianlancetaylor suggested for you.

Go rarely uses file descriptors, so it seems odd to pass a file descriptor to a function like this.

I was basing on the GetSize existing function: func GetSize(fd int) (width, height int, err error)

I'll check the options mentioned with someone on my team though to try to test if that would work for us. Thanks.

Using os.SameFile worked for us. Thanks.

OK, closing this proposal. Please comment if you disagree. Thanks.