Non blocking reads with Julia

Question

I would like to read an user input without blocking the main thread, much like the getch() function from conio.h. Is it possible in Julia?

I tried with @async but it looked like my input wasn't being read although the main thread wasn't blocked.

Answer 1

The problem, I believe, is either you are running on global scope which makes @async create its own local variables (when it reads, it reads into a variable in another scope) or you are using an old version of Julia.

The following examples read an integer from STDIN in a non-blocking fashion.

function foo()
    a = 0
    @async a = parse(Int64, readline())
    println("See, it is not blocking!")
    while (a == 0)
        print("")
    end
    println(a)
end

The following two examples do the job in global scope, using an array. You can do the same trick with other types mutable objects. Array example:

function nonblocking_readInt()
    arr = [0]
    @async arr[1] = parse(Int64, readline())
    arr
end

r = nonblocking_readInt() # is an array
println("See, it is not blocking!")
while(r[1] == 0) # sentinel value check
    print("")
end
println(r[1])