Snippet with fzf fails with "Failed to read /dev/tty"

[denisidoro]

The following cheatsheet fails:

% fzf

# call fzf
fzf

I have already tried all tricks with exec, stty, < /dev/tty and so on. Help needed.

[DenSA-Inc]

Your problem is the way linux handles tty's. Terminals are created by calls to openpty which creates something of a pipe that goes through the kernel terminal driver. The driver is responsible for turning ctrl-c into a SIGINT etc. Programs detect the presense of a terminal with isatty which does some ioctl-calls and queries information associated with the file descriptor of stdin.

My guess is that running a command with spawn() (don't you need to call wait() on the child process?) does not "carry over" the terminal information of stdin. One solution is calling exec on unix systems, but this replaces the process's image with the command you're calling and you can't do this more than once. Another solution would be creating your own terminal with openpty and proxying information through them, but this would be too much work for something that could hide bugs.

I'll see if I can find something about rusts Command and terminals

[DenSA-Inc]

As a side note: exec is performed in the bash process you create in navi, therefore it can't take over navi. And < /dev/tty only works if the bash process is already connected to a terminal.

[DenSA-Inc]

I found the issue: rather than some complicated terminal magic not working as intended you missed a call to Child::wait(). I assume this way the Child struct gets dropped while the child process is still running. I'm not exactly sure what's supposed to happen then but adding the call to wait() fixed it. Maybe navi exited and closed the streams before fzf could read them.

I also performed a little test with a demo program that executed fzf without waiting for the child process. For some reason I got the fzf ui while my keypresses where sent to my shell and fzf seemingly at random. Sometimes I was able to narrow down fzf search results and sometimes I got autocompletion from my shell in the fzf ui.