In C, setting the timeout to '-1' for the `poll()` function will make it behave as a blocking call, meaning it will wait indefinitely until the file descriptor(s) or events being monitored become ready.
On the other hand, if you want to code a non-blocking `scanf()` function in C, you can use a combination of functions to achieve this. The key is to ensure that the program doesn't block while waiting for input. Here's an example of how you can do this using `select()`:
```c
#include <stdio.h>
#include <stdlib.h>
#include <sys/select.h>
#include <sys/time.h>
#include <sys/types.h>
int main() {
fd_set readfds;
struct timeval tv;
int ret;
while (1) {
// Set up the file descriptor set
FD_ZERO(&readfds);
FD_SET(STDIN_FILENO, &readfds);
// Set the timeout to 0 for non-blocking behavior
tv.tv_sec = 0;
tv.tv_usec = 0;
ret = select(STDIN_FILENO + 1, &readfds, NULL, NULL, &tv);
if (ret == -1) {
perror("select");
exit(1);
} else if (ret) {
if (FD_ISSET(STDIN_FILENO, &readfds)) {
char input[256];
if (fgets(input, sizeof(input), stdin) != NULL) {
printf("You entered: %s", input);
}
}
} else {
// No input is available
printf("No input available.\n");
}
}
return 0;
}
```
In this code:
1. We use `select()` to check if input is available on `stdin` without blocking. The timeout `tv` is set to zero.
2. If `select()` returns a value greater than 0, it means input is available, and we can use `fgets()` to read the input.
3. If `select()` returns 0, it means no input is available, so you can handle this case accordingly.
This code creates a non-blocking `scanf()`-like behavior. It continuously checks for input without blocking the program's execution. You can modify the handling of available input according to your specific requirements.