```{index} single: tiehash; SDBM_File function ``` ```{index} single: SDBM_File::tiehash; Perl function ``` # tiehash Open an SDBM database and return a blessed handle. Invoked by Perl when the user writes `tie %h, 'SDBM_File', $basename, $flags, $mode`. The five-argument form opens `$basename.dir` and `$basename.pag` using `sdbm_open`. The six-argument form (`tie %h, 'SDBM_File', $dirfile, $flags, $mode, $pagfile`) names the two files independently and uses `sdbm_prep` — useful with `File::Temp` handles. `$flags` takes the usual `Fcntl` constants: `O_RDONLY`, `O_WRONLY`, `O_RDWR`, optionally OR'd with `O_CREAT` to create a missing database. `$mode` is the permission bits applied (after umask) to newly created files; 0666 is the usual choice. Returns a blessed `SDBM_File` reference on success, or `undef` if the underlying open fails (with `$!` set to the reason).