---
name: "comcontrol"
section: "8"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/comcontrol"
---

# comcontrol(8)

control a special tty device

## NAME

**comcontrol** – control a special tty device

## DEPRECATION NOTICE

The **comcontrol** utility is deprecated and will be removed in FreeBSD 16.0.

## SYNOPSIS

**comcontrol** *special\_device* \[drainwait *number*\]

## DESCRIPTION

The **comcontrol** utility is used to examine and modify some of the special characteristics of the specified tty device. If no arguments other than the device (or "-" for stdin) are specified, it prints the settings of all controllable characteristics. This usage requires only read access on the device. Only the superuser can change the settings.

The following options are available:

- **drainwait** *number*

  Set the time to wait for output drain to the given number. The units are seconds. The default is 5 minutes, 0 means waiting forever. This option is needed mainly to specify an upper limit of minutes to prevent modem hanging.

The standard way to use **comcontrol** is to put invocations of it in the */etc/rc.d/serial* startup script.

## FILES

- */dev/ttyd?*

  dialin devices, hardwired terminals

- */dev/cuau?*

  dialout devices

## SEE ALSO

[stty(1)](/stty/1.md)

## HISTORY

Originally part of cgd's com package patches, version 0.2.1, to 386BSD-0.1. Once controlled bidirectional capabilities. Little is left to control now that these capabilities are standard.

## AUTHORS

Christopher G. Demetriou