How to use fzf remotely through SSH, within command substitution?

[FranklinYu]

This works as expected:

ssh -t example.com "echo -e 'a\nb' | fzf"

But I cannot capture the output with Command Substitution:

selected_value=$(ssh -t example.com "echo -e 'a\nb' | fzf")

Any idea why? And what’s the right usage?

[junegunn]

Do you have to run fzf remotely? If that is not the case, a simple workaround would be to run it locally.

selected_value=$(ssh example.com "echo -e 'a\nb'" | fzf)

[FranklinYu]

If I run it locally, does it mean that every preview command will be another SSH command? There are certainly workarounds (such as SSH multiplexing), but I’m curious why it doesn’t “Just Work”.

[junegunn]

Because ssh doesn't forward stderr and fzf renders its interface using stderr.

ssh -t example.com -c 'echo stderr >&2; echo stdout'

[FranklinYu]

I tried the command, and it behaves differently on my machines: both echo shows on terminal, but they are all on local stdout; for example if I do

ssh -t example.com 'echo stderr >&2; echo stdout' 2>/dev/null

I still see both of them. I then did some research, and it seems like OpenSSH always merge stdout and stderr when doing ssh -t. I guess I would have to use the aforementioned workaround. Thanks anyway!

(Note: in ssh, the -c flag means “choosing cipher”, not “command”.)

[junegunn]

(Note: in ssh, the -c flag means “choosing cipher”, not “command”.)

It was a typo. I missed sh while editing the command, so,

ssh -t example.com sh -c 'echo stderr >&2; echo stdout'

[dimo414]

Sorry to resurrect an old question @junegunn, but I'm curious if there's a less-simple workaround that doesn't require running fzf on the local machine. In my case I'm trying to execute a wrapper script that uses fzf remotely, and am hitting the same issue that ssh -t example.com my_fzf_wrapper works but selected_value=$(ssh -t example.com my_fzf_wrapper) does not.