How can I test whether stdin has input available in julia?

Question

I would like to detect whether there is input on stdin in a short time window, and continue execution either way, with the outcome stored in a Bool. (My real goal is to implement a pause button on a simulation that runs in the terminal. A second keypress should unpause the program, and it should continue executing.) I have tried to use poll_fd but it does not work on stdin:

julia> FileWatching.poll_fd(stdin, readable=true)
ERROR: MethodError: no method matching poll_fd(::Base.TTY; readable=true)

Is there a way that will work on julia? I have found a solution that works in python, and I have considered using this via PyCall, but I am looking for

1. a cleaner, pure-julia way; and
2. a way that does not fight or potentially interfere with julia's use of libuv.

Answer 1

bytesavailable(stdin)

Here is a sample usage. Note that if you capture the keyboard you also need to handle Ctrl+C yourself (in this example only the first byte of chunk is checked).

If you want to run it fully asynchronously put @async in front of the while loop. However if there will be no more code in this case this program will just exit.

import REPL
term = REPL.Terminals.TTYTerminal("xterm",stdin,stdout,stderr)
REPL.Terminals.raw!(term,true)
Base.start_reading(stdin)

while (true)
    sleep(1)
    bb = bytesavailable(stdin)
    if bb > 0
        data = read(stdin, bb)
        if data[1] == UInt(3)
            println("Ctrl+C - exiting")
            exit()
        end
        println("Got $bb bytes: $(string(data))")
    end
end