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Trap keypress in console.

Posted on 2001-08-19
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Last Modified: 2010-05-18
I need a method that waits x seconds for a user to press a key. If they key is pressed, it returns the character. If no key is pressed after x seconds, the method returns some non-character value (-1 perhaps?).

This method should run in a DOS application, not a windows application (the project I need the method for is intended to be run from AUTOEXEC.BAT).

I've attempted writing this myself but I'll be damned if I can work out how to do it. Every input command/method I've tried requires the user to press a key *and then press Enter*. This is no good to me; I want the program to wait for a single keystroke and if none is given to carry on anyway (with a different result).

100 points in anticipation of a quick answer; I get bored quickly and will give up if this takes too long.
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Question by:Subhuman
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8 Comments
 

Expert Comment

by:beyonddeath
ID: 6403310
Id recommend looping for x seconds and each time through the loop call kbhit() .. if it is true then theres a key waiting... if not and your loop ends... then no key was hit... if you do get a kbhit... and wanna know what it was... use getch().. it wont wait because you know there is somthing there...

Simple... ps .. I sure hope this wasnt homework ;-)
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Accepted Solution

by:
beyonddeath earned 400 total points
ID: 6403319
Im bored .. ill write the code;p
int x = 5; // seconds to wait
char got = -1;
time_t = time(NULL);
for(;time(NULL)-time_t <= x ; )
{
 if(kbhit)
{
got = getch();
break;
}
}


0
 
LVL 1

Author Comment

by:Subhuman
ID: 6403321
Heh, nope. If it was homework it'd be in Java and I wouldn't need to ask for something this simple. :)

kbhit() ... What header to I need to include for that? Makes it easier finding the docs for it if I know where to look. :)
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Expert Comment

by:beyonddeath
ID: 6403329
conio.h ;p... (i cant beleive i can actually answer one of these questions)... that is in vc++ 6
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Expert Comment

by:beyonddeath
ID: 6403330
and as i check turbo c++... so itll work in dos...
0
 
LVL 1

Author Comment

by:Subhuman
ID: 6403331
Ooh, thanks. :) Missed that before posting.

*copies and pastes into notepad for testing on other computer*
0
 
LVL 7

Expert Comment

by:peterchen092700
ID: 6403438
additional comment:

to correctly support extended key codes (like functions keys etc) you should use:

int got = -1;  // use int, not char
...
if(kbhit)
{
got = getch();
if (!got) {
  // extended key code "waiting" in keyboard buffer
  got = getch() << 8;
}
break;
}


Peter

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LVL 1

Author Comment

by:Subhuman
ID: 6404549
Thanks, works like a charm. :)

Thanks for the tip too, peterchen. :)

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