# Libtmux.Formats.lookup

- **Module:** Libtmux
- **Package:** libtmux
- **Language:** OCaml
- **Kind:** function
- **Source:** https://github.com/libtmux/libtmux-ocaml/blob/205dfda49742592b479247049d186956e4a4cfe9/lib/libtmux.mli#L549
- **Public owner:** Libtmux
- **Page:** https://libtmux.org/en/ocaml/latest/reference/libtmux-formats-lookup/

```
val lookup :
  version:string -> observation -> string -> (state, Error.t) result
```

No I/O. Supply the version recorded by the acquiring client's `version` accessor. Unsupported catalog versions return an error. Native typed accessors remain the primary API; lookup does not acquire extra fields.

## Parameters

- `version` (`string`)
- `arg1` (`observation`)
- `arg2` (`string`)

## Guides

Pages that discuss `lookup`.

- [Compatibility](/en/ocaml/latest/guides/compatibility/)