Comment by mpyne
5 hours ago
> The stdin-vs-stdout split is where I see the most actual "is this a TTY" mistakes though. Tools that emit JSON-on-stdout-when-piped and TUI-when-not work fine until something stuffs them into a PTY with piped stdin — then they're in TUI mode but can't actually read the user input format they expect.
Stuff like this is why a build script I used to maintain would redirect stdin from /dev/null when running commands that were intended to be non-interactive. You only need one script to hang forever waiting for a user to type in a password to decide that you'll force the issue going forward.
Same problem flipped: I once watched a CI step hang for 47 minutes because some sub-command popped a `read -p "Continue?"` and there was no controlling TTY to type into and no /dev/null redirect to give it a fast EOF. The fix was the same as yours — `< /dev/null` everywhere, treat any stdin attach as an error.
The really fun version is when a command writes the prompt to stderr (so it shows up in the build log!) and then reads from a stdin you didn't realize was still open. Took embarrassingly long to track down.