# tmux.CommandTrace.Err

- **Module:** tmux.CommandTrace
- **Package:** github.com/libtmux/libtmux-go/tmux
- **Language:** Go
- **Kind:** attribute
- **Source:** https://github.com/libtmux/libtmux-go/blob/52968a3181c1c9e6d1b26c565d4b170968ae61c0/tmux/observer.go#L47
- **Page:** https://libtmux.org/en/go/latest/reference/tmux-commandtrace-err/

Err is the transport or validation failure, if any. A completed tmux command that failed leaves this nil and reports through ExitCode.