ERR_FILE_IO
err(ERR_FILE_IO, "%s: open", basedir_abs);
err(ERR_FILE_IO, "%s/%s: openat", basedir_abs, f->path);
err(ERR_FILE_IO, "%s: openat", f->path);
err(ERR_FILE_IO, "%s: copy file", f->path);
err(ERR_FILE_IO, "%s: asprintf", fargs->sink);
err(ERR_FILE_IO, "%s: mkpath", tofree);
err(ERR_FILE_IO, "%s: open", root);
err(ERR_FILE_IO, "%s: openat", root);