diff --git a/hash-pipe.c b/hash-pipe.c
index 17b7119..f1894f5 100644
--- a/hash-pipe.c
+++ b/hash-pipe.c
@@ -10,7 +10,7 @@
 #define BUF_SIZE 4096
 
 void print_usage (void) {
-	printf("Usage:\n"
+	dprintf(STDERR_FILENO, "Usage:\n"
 "\n"
 "  hash-pipe ALGORITHM FILENAME LOGFILE\n"
 "\n"
@@ -35,7 +35,7 @@ int main (int argc, char **argv) {
 	 */
 	const EVP_MD *md = EVP_get_digestbyname(algo_name);
 	if (md == NULL) {
-		printf("Unknown algorithm: %s\n", algo_name);
+		dprintf(STDERR_FILENO, "Unknown algorithm: %s\n", algo_name);
 		exit(1);
 	}
 	
@@ -44,7 +44,7 @@ int main (int argc, char **argv) {
 	 */
 	int fd = open(log_name, O_WRONLY | O_APPEND | O_CREAT, 0644);
 	if (fd == -1) {
-		printf("Unable to open file for writing: %s\n", log_name);
+		dprintf(STDERR_FILENO, "Unable to open file for writing: %s\n", log_name);
 	}
 	
 	EVP_MD_CTX *mdctx = EVP_MD_CTX_new();
@@ -57,7 +57,7 @@ int main (int argc, char **argv) {
 		s = read(STDIN_FILENO, buf, BUF_SIZE);
 		
 		if (s == -1) {
-			printf("NFG\n");
+			dprintf(STDERR_FILENO, "Unknown error.\n");
 			exit(1);
 		} else if (s == 0) {
 			break;