- fwrite(start, size, 1, file);
+ if (!file) {
+ fprintf(stderr, "Could not open '%s' for writing: ", filename);
+ perror("");
+ return 1;
+ }
+
+ if (fwrite(start, size, 1, file) != 1) {
+ fprintf(stderr, "Could not write to '%s': ", filename);
+ perror("");
+ return 1;
+ }
+