Check file handle in C using system calls

chp2/poll.c

@@ -0,0 +1,38 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <poll.h>
+
+#define TIMEOUT 5  /* poll timeout, in seconds */
+
+int main(void) {
+	struct pollfd fds[2];
+	int ret;
+
+	/* watch stdin for input */
+	fds[0].fd = STDIN_FILENO;
+	fds[0].events = POLLIN;
+
+	/* watch stdout for ability to write (almost always true) */
+	fds[1].fd = STDOUT_FILENO;
+	fds[1].events = POLLOUT;
+
+	/* All set, block! */
+	ret = poll(fds, 2, TIMEOUT * 1000);
+	if (ret == -1) {
+		perror("poll");
+		return 1;
+	}
+
+	if (!ret) {
+		printf("%d seconds elapsed.\n", TIMEOUT);
+		return 0;
+	}
+
+	if (fds[0].revents & POLLIN)
+		printf("stdin is readable\n");
+	
+	if (fds[1].revents & POLLOUT)
+		printf("stdout is writable\n");
+
+	return 0;
+}