How Stdin/Stdout used by fzf?

[antonmedv]

Hi,

Question: how fzf manage to write the result to stdout but still open interactive TUI in alt screen?

How this is done? ls | fzf | cat

Thanks.

[junegunn]

The example is misleading, you should remove $(...) and change echo to cat to make your point.

ls | fzf | cat

Having said that, to answer the original question, fzf prints its UI to STDERR instead of STDOUT.

[antonmedv]

Ohh. Nice))

[antonmedv]

I didn’t thought about it. Thanks for answering.

[leiless]

Hi, @junegunn. Does the fzf always print the tui in STDERR, or in some specific conditions?

[leiless]

Update: After grep-ing the src/tui folder, I found that the STDERR seems solely used in displaying the tui?

[junegunn]

Always.

[manyids2]

Hi,
To follow up, how does fzf read from STDIN for user input while a long running command is piped to it?
New to TUI, so assuming the pipe writes to STDIN of fzf, it should be blocked till STDIN is drained?
For example
ls -R / | fzf

[junegunn]

fzf reads /dev/tty directly.

[manyids2]

Oh ok! Thank you for replying!

Out of context, but you're a genius! Thank you so much for fzf!