Code:
/* play_again3.c
* purpose: ask if user wants another transaction
* method: set tty into chr-by-chr, no-echo mode
* set tty into no-delay mode
* read char, return result
* returns: 0=>yes, 1=>no, 2=>timeout
* better: reset terminal mode on Interrupt
*/
#include <stdio.h>
#include <termios.h>
#include <fcntl.h>
#include <string.h>
#define ASK "Do you want another transaction"
#define TRIES 3 /* max tries */
#define SLEEPTIME 2 /* time per try */
#define BEEP putchar('\a') /* alert user */
main()
{
int response;
tty_mode(0); /* save current mode */
set_cr_noecho_mode(); /* set -icanon, -echo */
set_nodelay_mode(); /* noinput => EOF */
response = get_response(ASK, TRIES); /* get some answer */
tty_mode(1); /* restore orig mode */
return response;
}
get_response( char *question , int maxtries)
/*
* purpose: ask a question and wait for a y/n answer or maxtries
* method: use getchar and complain about non-y/n input
* returns: 0=>yes, 1=>no, 2=>timeout
*/
{
int input;
printf("%s (y/n)?", question); /* ask */
fflush(stdout); /* force output */
while ( 1 ){
sleep(SLEEPTIME); /* wait a bit */
input = tolower(get_ok_char()); /* get next chr */
if ( input == 'y' )
return 0;
if ( input == 'n' )
return 1;
if ( maxtries-- == 0 ) /* outatime? */
return 2; /* sayso */
BEEP;
}
}
/*
* skip over non-legal chars and return y,Y,n,N or EOF
*/
get_ok_char()
{
int c;
while( ( c = getchar() ) != EOF && strchr("yYnN",c) == NULL )
;
return c;
}
set_cr_noecho_mode()
/*
* purpose: put file descriptor 0 into chr-by-chr mode and noecho mode
* method: use bits in termios
*/
{
struct termios ttystate;
tcgetattr( 0, &ttystate); /* read curr. setting */
ttystate.c_lflag &= ~ICANON; /* no buffering */
ttystate.c_lflag &= ~ECHO; /* no echo either */
ttystate.c_cc[VMIN] = 1; /* get 1 char at a time */
tcsetattr( 0 , TCSANOW, &ttystate); /* install settings */
}
set_nodelay_mode()
/*
* purpose: put file descriptor 0 into no-delay mode
* method: use fcntl to set bits
* notes: tcsetattr() will do something similar, but it is complicated
*/
{
int termflags;
termflags = fcntl(0, F_GETFL); /* read curr. settings */
termflags |= O_NDELAY; /* flip on nodelay bit */
fcntl(0, F_SETFL, termflags); /* and install 'em */
}
/* how == 0 => save current mode, how == 1 => restore mode */
/* this version handles termios and fcntl flags */
tty_mode(int how)
{
static struct termios original_mode;
static int original_flags;
if ( how == 0 ){
tcgetattr(0, &original_mode);
original_flags = fcntl(0, F_GETFL);
}
else {
tcsetattr(0, TCSANOW, &original_mode);
fcntl( 0, F_SETFL, original_flags);
}
}
