timothyb89 / crossterm-stdin-test

Reading from both stdin and tty in crossterm

Attempts to read piped input from stdin in an interactive terminal interface using crossterm.

crossterm v0.8

In crossterm 0.8, it's possible to read from standard input (e.g. data to process) and still receive separate tty input events (e.g. keypresses for an interactive terminal UI).

See crossterm-0.8.2 for an example:

cd crossterm-0.8.2/
cargo build

for i in $(seq 1 100); do echo $i; sleep 1; done | ./target/debug/crossterm-stdin-test 2> err.log

This works because piped content (in this case, output from the shell's counting loop) is read from /dev/stdin, while crossterm reads terminal input (keypresses) from /dev/tty.

There are a few issues minor issues with this approach:

• we can't read from rust's usual std::io::stdin as it EOFs when crossterm enables raw mode and can't be reopened; the manual read from the /dev/stdin file works around this

  This hack should work on all UNIXes and has been tested on Linux and macOS.

• if no content is piped in (i.e. just running ./target/debug/crossterm-stdin-test), both /dev/stdin and /dev/tty seem to be the same file and the two readers fight over reading each character.

  TUI apps can work around this by checking if stdin is a tty using atty, e.g. atty::is(Stream::Stdin), and leaving /dev/stdin closed if so.

• Windows doesn't seem to have any issues reading from rust's normal stdin so this hack isn't needed

crossterm v0.10

crossterm's API changed slightly since v0.8, but an equivalent program now results in an error:

cd crossterm-0.10.1/
cargo build

for i in $(seq 1 100); do echo $i; sleep 1; done | ./target/debug/crossterm-stdin-test 2> err.log

The program will exit immediately and err.log will contain:

error opening raw mode: Os { code: 25, kind: Other, message: "Inappropriate ioctl for device" }

Minimal reproduction

The minimal reproduction just tries to enable raw mode. If you pipe content in, it prints the same error:

cd crossterm-0.10.1-minimal/

cargo build

echo '' | ./target/debug/crossterm-stdin-test

...fails and outputs the same message