Add `flush` method to I/O input types

[3442853561]

There should be flush () for input
Just like the getch() function in C language

[oli-obk]

Do you mean that StdIn should flush StdOut before reading? Please elaborate with examples of what you expect to happen.

You can find details on how to do it manually on stackoverflow

[3442853561]

@oli-obk I hope to be able to read the input before the enter
like getch() in C language

[oli-obk]

There's several crates that allow you to do this: http://stackoverflow.com/questions/26321592/how-can-i-read-one-character-from-stdin-without-having-to-hit-enter/27335584#27335584

If you think they belong into the standard library, I suggest you create an RFC to move some functionality from a crate to libstd.

[3442853561]

rust-lang/rfcs#1885

[sfackler]

Closing in favor of the rfcs issue.