entropy-watcher: Print difference

1 files changed, 12 insertions, 6 deletions

diff --git a/entropy-watcher.c b/entropy-watcher.c
index 2d6fe86..6dc1b89 100644
--- a/entropy-watcher.c
+++ b/entropy-watcher.c
@@ -1,7 +1,8 @@
 /**
- * Watch available kernel entropy. By default, it prints the available entrophy
- * every second, but this can be changed with arg1 (in milliseconds). You can
- * also press Enter to immediately print the current entrophy.
+ * Watch available kernel entropy. By default, it prints the available entropy
+ * and difference to the previously recorded entropy every second, but this can
+ * be changed with arg1 (in milliseconds). You can also press Enter to
+ * immediately print the current entropy.
  *
  * Author: Peter Wu <lekensteyn@gmail.com>
  * Date: 2013-01-28
@@ -21,6 +22,7 @@ int main(int argc, char **argv) {
 	struct pollfd pfd;
 	int fd;
 	int print_interval_ms;
+	long int avail, prev = 0;
 
 	print_interval_ms = 1000;
 	if (argc > 1) {
@@ -37,7 +39,12 @@ int main(int argc, char **argv) {
 	pfd.events = POLLIN;
 
 	while ((r = read(fd, buff, sizeof(buff))) > 0) {
-		write(STDOUT_FILENO, buff, r - 1);
+		/* remove possible newline and terminate string for sure */
+		buff[r - 1] = 0;
+		avail = strtol(buff, NULL, 10);
+		printf("%li (%+li)", avail, avail - prev);
+		prev = avail;
+
 		poll(&pfd, 1, print_interval_ms);
 		lseek(fd, 0, SEEK_SET);
 		if (pfd.revents == POLLIN) { /* pressed enter? */
@@ -45,8 +52,7 @@ int main(int argc, char **argv) {
 			if (r > 0 && buff[r - 1] == '\n')
 				continue;
 		}
-		buff[0] = '\n';
-		write(STDOUT_FILENO, buff, 1);
+		putchar('\n');
 	}
 
 	close(fd);