Stop only if some key is pressed in C - c

Question

If I had a while loop that I wanted to stop only if the q key is pressed how would I do that.
However, I do NOT want it to quite the program
#define TRUE 1
#define FALSE 0
typedef int boolean;
int main(int argc,char* argv[]){
char *script = malloc(MAXPATH);
script = "ls";
boolean a;
a = TRUE;
while(a){ //this is the while loop i want to break incase of a keypress
system(script);
}
do something else
something else....
This will be running on Mac OS X.
both getchar() and getc() pause for a response which makes loop stop

Answer 1

you can use select() mechanism in UNIX-LIKE OS.
all in one function:
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/select.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
fd_set readfds;
struct timeval tv;
int ch;
int bool, ret;
FD_ZERO(&readfds);
bool = 1;
while (bool) {
FD_SET(STDIN_FILENO, &readfds);
tv.tv_sec = 0;
tv.tv_usec = 0;
/* int select(int nfds, fd_set *readfds, fd_set *writefds,
* fd_set *exceptfds, struct timeval *timeout); */
ret = select(STDIN_FILENO + 1, &readfds, NULL, NULL, &tv);
if (ret < 0) {
perror("select error");
exit(1);
} else if (ret == 0) {
/* timeout */
} else if (FD_ISSET(STDIN_FILENO, &readfds)) {
ch = fgetc(stdin);
if (ch == 'q') {
bool = 0;
}
}
sleep(1);
fprintf(stderr, ".");
}
return 0;
}

Answer 2

native functions in C with which i can detect a keypress are :
getchar() and getc()
kbhit() is a function returns integer value whenever the key is pressed
you can use the above functions
#include <stdio.h>
#include <conio.h>
#include <math.h>
#include <time.h>
int main()
{
int m;
clrscr();
do
{
if(kbhit())
{
if((m=getch())==97)
{
printf("Key a is pressed....\n");
}
}
} while(1);
getch();
return 0;
}

Answer 3

I'm glad of alexchandel's answer. I had never heard of poll()
poll() is a good answer for POSIX style systems like the questioner's platform
_kbhit() is the simplest answer on MS Windows. Their Poll() is different of course
The 1 means just one descriptor block in my list, the 100 is milliseconds timout
my file handle is { 0, for stdin
read the man page for the many events you can interrogate, I only wanted POLLIN
#include <stdio.h>
#include <poll.h>
#include <errno.h>
static struct pollfd attention = { 0, POLLIN } ;
int main()
{
int x, y;
for (;;)
{
x = poll(&attention, 1, 100);
if (x < 0)
{
printf("problem %d\n", errno);
break;
}
else if (x)
{
printf("you rang %x ?", x);
y = getc(stdin);
printf(" %c of course\n", y);
if (y == '.') break;
}
}
return 0;
}

Answer 4

You could make the computation run in a pthread while the main loop reads char on stdin. SDL library has better input controls if you don't just want to read char from stdin. gtk also has events that the window receives. The command "xev" is a xlib program for linux that works similarly. It opens a blank window and it reads key events as they come.