tail head cat sleep
QR code linking to this page

Manual Pages  — COMCONTROL


comcontrol – control a special tty device



comcontrol special_device [dtrwait number] [drainwait number]


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:
dtrwait number
  Set the time to wait after dropping DTR to the given number. The units are hundredths of a second. The default is 300 hundredths, i.e., 3 seconds. This option needed mainly to set proper recover time after modem reset.
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 needed mainly to specify 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.


  dialin devices, hardwired terminals
  dialout devices


stty(1), sio(4)


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


Christopher G. Demetriou

COMCONTROL (8) May 15, 1994

tail head cat sleep
QR code linking to this page

Please direct any comments about this manual page service to Ben Bullock. Privacy policy.

Our grievance is not just against Unix itself, but against the cult of Unix zealots who defend and nurture it. They take the heat, disease, and pestilence as givens, and, as ancient shamans did, display their wounds, some self-inflicted, as proof of their power and wizardry. We aim, through bluntness and humor, to show them that they pray to a tin god, and that science, not religion, is the path to useful and friendly technology.
— The Unix Haters' handbook