C IO question

blackzone · 07-15-2006, 04:56 PM

Is there anyway to get one character at a "without" the need to press "enter".

For example, if you type "abc", the below program will display "abc\nabc".

But I want it to display "aabbcc"

Code:

#include <stdio.h>

int main()
{
  char ch;

  ch = getchar(  );
  while( 1 ) {
   putc(ch, stdout);
   ch = getchar( );
  }
}

raskin · 07-15-2006, 05:22 PM

man setvbuf.
Did it help?

blackzone · 07-15-2006, 08:48 PM

Quote:

Originally Posted by raskin

man setvbuf.
Did it help?

ya it does. It point me to read about different buffering type in linux and lead me to find the below code.

It seemed you have to use low level IO to do it.

Code:

#include <termios.h>
#include <unistd.h>
#include <assert.h>
#include <string.h>
/*------------------------------------------------*/
int getch(void) {
      int c=0;

      struct termios org_opts, new_opts;
      int res=0;
          //-----  store old settings -----------
      res=tcgetattr(STDIN_FILENO, &org_opts);
      assert(res==0);
          //---- set new terminal parms --------
      memcpy(&new_opts, &org_opts, sizeof(new_opts));
      new_opts.c_lflag &= ~(ICANON | ECHO | ECHOE | ECHOK | ECHONL | ECHOPRT | ECHOKE | ICRNL);
      tcsetattr(STDIN_FILENO, TCSANOW, &new_opts);
      c=getchar();
          //------  restore old settings ---------
      res=tcsetattr(STDIN_FILENO, TCSANOW, &org_opts);
      assert(res==0);
      return(c);
}

crabboy · 07-15-2006, 10:12 PM

Your code is the correct and best way to modify the terminal behavior. Most terminals by default are in canonical mode which requres you to press enter before it processes the input, setting -ICANON allows the input to be processed almost immediately.