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astropirhana

09-01-2006 02:41 PM

C getc without CR

I am trying to get input from the keyboard character by character.

I am writing my code in C.

The problem with getc and fgetc are that they force the user to enter a carriage return and then all buffered characters appear to be returned one at a time and processed. I want to process them immediatly not waiting for the carriage return key to be struck.

I found some code that mimmics the dos command kbhit().

http://www.linux-sxs.org/programming/kbhit.html

This code almost works 100%...actually 95%.

There are a few bugs. I am using it, and it is working alright. I have to work around a few shortcomings.

What is the recommended way to do this with Linux?

Astro

tuxdev

09-01-2006 03:05 PM

getc and fgetc aren't why buffering happens. Buffering is a file stream attribute.
You can switch to raw mode by doing

Code:

struct termios cur,raw;

tcgetattr(STDIN_FILENO,&cur);  // get current mode to restore later

raw=cur;

raw.c_lflag&=~(ICANON|ECHO|ISIG);

raw.c_cc[VMIN]=1;

raw.c_cc[VTIME]=0;

tcsetattr(STDIN_FILENO,TCSAFLUSH,&raw);

then return it to cooked mode by doing

Code:

tcsetattr(STDIN_FILENO,TCSAFLUSH,&cur);

You will need to #include <termios.h>

astropirhana

09-01-2006 03:12 PM

Thanks alot

Worked great!

Astro

jlliagre

09-01-2006 03:21 PM

tuxdev is actually suggesting the same solution you already use with kbhit.

What are the 5% cases where you observe it doesn't work ?

KenJackson

09-01-2006 03:40 PM

Quote:

Originally Posted by jlliagre

tuxdev is actually suggesting the same solution you already use with kbhit.

Actually, there was one difference.

Quote:

Originally Posted by kbhit

tcsetattr(0, TCSANOW, &new_settings);

Quote:

Originally Posted by tuxdev

tcsetattr(STDIN_FILENO,TCSAFLUSH,&raw);

TCSANOW changes immediately, TCSAFLUSH discards input already received. It's not clear if this will make any difference for stdin though.

tuxdev

09-01-2006 04:03 PM

Oh yeah, didn't read that. I guess the difference might be that in this case, the simplicity of using the main library directly causes less errors than complicated mystery code in a library.

Edit: didn't refresh page to see newer comment. I'm not sure if it makes a difference, I pulled that more or less from the code example in Advanced Programming in the Unix Enviroment, originally used in a homework assignment.

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