DOKK / manpages / debian 12 / detachtty / attachtty.1.en
DETACHTTY(1) General Commands Manual DETACHTTY(1)

detachtty, attachtty - run an interactive program with io to a unix-domain socket

detachtty [--no-detach] [--dribble-file  dribblename] [--log-file  name] [--pid-file  pidname] socket-path command [arguments-to-command]...
attachtty socket-path [command] [timeout]
attachtty username@host:socket-path [command]

detachtty lets you run interactive programs non-interactively, and connect to them (optionally over the network) when you do need to interact with them. command is run on a pseudo-terminal, and data is copied between it and a unix(7)-domain socket named socket-path. command runs with the current user's permissions and environment variables.

attachtty is used to connect to a process running under detachtty. It copies between socket-path and stdin/out. It also catches SIGINT and arranges for it to be forwarded to the command, so the user may use Control-C in the usual fashion.

If you've used screen, it's a similar concept. Compared to screen, detachtty has

* no capability to swap between different screens (it doesn't co-opt C-a)

* no tty emulation (you can sanely use it in emacs comint modes)

* no features (less to go wrong)

* no configuration file

* ability to spawn ssh to securely connect across the network

These programs approximately follow the usual GNU command line syntax, using long options that start with two dashes (`--').

For detachtty, the options are:

Don't fork into the background. Useful if you wish to start the program from inittab(5).
All input from and to the program being run is copied into dribblename (if unspecified, it is discarded).
Status messages (client connects, disconnects, errors) are sent to name (if unspecified, they go to standard error).
The process ID of detachtty is written to pidname. See SIGNALS.
The unix-domain socket. If access to command should be in any way restricted, so should this socket - i.e. it is recommended that you put it in a mode 700 directory.
The command to run (which is searched for in the normal way). All remaining command line parameters are passed to it as arguments.

For attachtty, the options are instead:

This is either the path to socket-path, or a "remote path" of the form username@host:socket-path where username@host is passed to ssh. The latter form is currently an alias for ssh -t username@host attachtty socket-path [text] and lets ssh manage the authentication, i.e. whether to ask for a password or not.
The text to write into the socket. It will be processed by the command executed from detachtty. For local sockets, the same effect can be obtained with (echo -e text´\r´; sleep timeout) | attachtty socket-path
The maximum timeout in seconds (defaults to 1) to wait for the written text to be processed. This is available only for local connections.

To detach from the tty without exiting from the server process, send attachtty any signal that it doesn't catch. See the SIGNALS section.

detachtty does not search the user's PATH environment variable for the program to execute, so a full pathname must be provided.

If you get an immediate "Child terminated, exiting" message from detachtty, this usually means that the program you specified was not found or could not be executed (on Linux 2.4, execve(1) succeeds even if it didn't, so to speak).

You will probably go insane a lot more slowly if you use absolute pathnames for all filename arguments.

Sending SIGHUP to the process identified by pidname will cause detachtty to close and reopen its log files.

Sending SIGTSTP to an attachtty process (usually from the keyboard with ^Z) will cause it to stop itelf, leaving the server process running. It can be resumed normally with the shell builtin command "fg".

Sending SIGQUIT to an attachtty process (usually from the keyboard with ^\) will cause it to detach from the tty and quit, leaving the server process running. Sometimes you need to press it twice.

screen(1), ssh(1), sbcl(1).

Written by Daniel Barlow <>, and a cast of units. Modified by Luca Capello <>. Modified by Mark Huetsch <>. Modified by Massimiliano Ghilardi <>.

March 18, 2006