diff --git a/b2/boom.c b/b2/boom.c
index d3dde4a..b575ab5 100644
--- a/b2/boom.c
+++ b/b2/boom.c
@@ -18,6 +18,22 @@
 #include "lang.h"
 
 
+static void open_stdin(const char *name)
+{
+	int fd;
+
+	fd = open(name, O_RDONLY);
+	if (fd < 0) {
+		perror(name);
+		exit(1);
+	}
+	if (dup2(fd, 0) < 0) {
+		perror("dup2");
+		exit(1);
+	}
+}
+
+
 static void usage(const char *name)
 {
 	fprintf(stderr, "usage: %s [file]\n", name);
@@ -27,21 +43,11 @@ static void usage(const char *name)
 
 int main(int argc, char **argv)
 {
-	int fd;
-
 	switch (argc) {
 	case 1:
 		break;
 	case 2:
-		fd = open(argv[1], O_RDONLY);
-		if (fd < 0) {
-			perror(argv[1]);
-			exit(1);
-		}
-		if (dup2(fd, 0) < 0) {
-			perror("dup2");
-			exit(1);
-		}
+		open_stdin(argv[1]);
 		break;
 	default:
 		usage(*argv);