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Getchar() loop

  1. Apr 20, 2009 #1
    If you use getchar() to capture a character and then print it to the stdout in a loop,
    why does it first capture the characters in the list (up to whatever max) and then print them all at once?

    In other words, how would I echo every character one at a time using a getchar() loop?
     
  2. jcsd
  3. Apr 20, 2009 #2
  4. Apr 20, 2009 #3

    rcgldr

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    Try _getch() instead.
     
  5. Apr 20, 2009 #4
    Is _getch() available everywhere?

    What is happening to you I think is that you need to flush stdout. In C if you write to a file buffer (stdout is a kind of file buffer) it will buffer a bunch of writes and then write them all at once, for efficiency. "Flushing" forces the write-everything-buffered-at-once operation to happen earlier.

    Try putting:
    fflush(stdout);
    After putch.
     
  6. Apr 20, 2009 #5
    that just reads without echoing (i.e. w/o printing strokes on screen)
     
  7. Apr 20, 2009 #6
    Coin, the fflush didn't work.

    good guess though
     
  8. Apr 20, 2009 #7

    Hurkyl

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    On many (most? all?) systems, your program isn't given any of the characters until you press enter. You need to use some system-specific API if you want to trap individual keystrokes.
     
  9. Apr 20, 2009 #8
    system-specific API?

    idk what that is, but yea it only works after pressing enter
     
  10. Apr 20, 2009 #9

    Hurkyl

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    Yah. Things like the _getch() function in the Windows API Jeff mentioned. I believe the curses library (*NIX systems) has a similar function.

    And, of course, any API that lets you make windows and stuff should have ways to get keypresses.
     
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