# libtmux::OptionEntry::index

- **Module:** libtmux::OptionEntry
- **Package:** libtmux-cxx
- **Language:** C++
- **Kind:** attribute
- **Source:** https://github.com/libtmux/libtmux-cxx/blob/393d4b0ad666f18a6581f1eb281741a75a7503f0/include/libtmux/options.hpp#L35
- **Page:** https://libtmux.org/en/cxx/latest/reference/libtmux-optionentry-index/

Present only for array options, which tmux indexes sparsely: absent indexes are genuinely unset rather than empty.