Übung 5

Assets/Betriebssysteme_uebung/u6-a2-anlage/helpers.c

@@ -0,0 +1,103 @@
+/*
+ * This is just some code behind the curtain.
+ * You really don't need to touch this.
+ *
+ */
+
+#include <stdio.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include "helpers.h"
+
+int do_quit = 0;
+int do_reload = 0;
+
+int load_config(void) {
+	static char firsttime_message[] = "Loading";
+	static char subsequent_message[] = "Reloading";
+	static char *message = firsttime_message;
+
+	fprintf(stderr, "%s configuration... ", message);
+	fprintf(stderr, "done.\n");
+
+	message = subsequent_message;
+	do_reload = 0;
+
+	return 1;
+}
+
+int main_loop(void) {
+	fd_set rfds;
+	struct timeval tv;
+	int retval;
+	char buf[1024];
+	ssize_t len;
+
+#if 0
+	/* fork() to the background */
+	if(fork()) return 0;
+#endif
+
+	fprintf(stderr, "I'm just a simple daemon, my PID is: %i\n",
+		getpid());
+
+	while (!do_quit) {
+		/* 
+		 * Let's just do our really simple job:
+		 * Copy stdin to stdout (just another cat(1)).
+		 */
+
+		if (do_reload) {
+			load_config();
+		}
+
+		/* Watch stdin (fd 0) to see when it has input. */
+		FD_ZERO(&rfds);
+		FD_SET(0, &rfds);
+
+		/* Wait up to five seconds. */
+		tv.tv_sec = 5;
+		tv.tv_usec = 0;
+
+		retval = select(1, &rfds, NULL, NULL, &tv);
+		/* Don't rely on the value of tv now! */
+
+		if (retval == -1) {
+			if (errno == EINTR) {
+				continue;
+			}
+
+			perror("select()");
+			continue;
+		}
+
+		if (retval == 0) {
+			/* fprintf(stderr, "Timeout reached.\n"); */
+			continue;
+		}
+
+		if (!FD_ISSET(0, &rfds)) {
+			fprintf(stderr, "BUG: Empty read-set, this should"
+				" never happen. Never ever. Really! :-)\n");
+			continue;
+		}
+
+		len = read(0, buf, sizeof(buf) - 1);
+		if (len < 0) {
+			perror("read()");
+			continue;
+		}
+
+		buf[len] = 0;
+		printf("%s", buf);
+
+		if (len == 0) {
+			do_quit = 1;
+		}
+	}
+
+	return 1;
+}