shell: use amount of bytes returned from mufs_read()

source/shell/mufs.c

@@ -159,6 +159,7 @@ int shell_cat(struct console *con, size_t argc, const char **argv)
 {
 	char data[256];
 	struct mufs_file *file;
+	size_t ret;
 
 	if (argc < 1) {
 		fprintf(con->fp, "usage: mufs cat <path>\n");
@@ -175,8 +176,8 @@ int shell_cat(struct console *con, size_t argc, const char **argv)
 		return -1;
 	}
 
-	while (mufs_read(file, data, sizeof data) != 0) {
-		fwrite(data, sizeof *data, sizeof data, con->fp);
+	while ((ret = mufs_read(file, data, sizeof data)) != 0) {
+		fwrite(data, sizeof *data, ret, con->fp);
 	}
 
 	mufs_close(file);