Bash – Start a process on a different tty

bashtty

After about an hour of Googling this, I can't believe nobody has actually asked this question before…

So I've got a script running on TTY1. How do I make that script launch some arbitrary program on TTY2?

I found tty, which tells you which TTY you're currently on.
I found writevt, which writes a single line of text onto a different TTY.
I found chvt, which changes which TTY is currently displayed.

I don't want to display TTY2. I just want the main script to continue executing normally, but if I manually switch to TTY2 I can interact with the second program.

Best Answer

setsid sh -c 'exec command <> /dev/tty2 >&0 2>&1'

As long as nothing else is using the other TTY (/dev/tty2 in this example), this should work. This includes a getty process that may be waiting for someone to login; having more than one process reading its input from a TTY will lead to unexpected results.

setsid takes care of starting the command in a new session.

Note that command will have to take care of setting the stty settings correctly, e.g. turn on "cooked mode" and onlcr so that outputting a newline will add a carriage return, etc.

Related Solutions

Freebsd – How to you get console backgrounds for Arch Linux

To get rid off the boot image: On other distros the idea is the same -> splash=no in boot kernel commandline or change the picture in /etc/bootsplash or equivalent.

On open suse 11.4 (and probably some earlier versions of suse) you can get rid of that background picture by using Yast on command line as follows:

System -> Boot Loader -> From boot images choose the one already marked -> Edit -> Optional kernel Command line parameters: change -> splash=no after that you have a professional black background as it should be.

To change this tty background picture to something nice:

Find this directory -> /etc/bootsplash/themes/opensuse/images and replace the file with your screen size to something you like. Don't change the file name! Just put something else there with that same name. In same size, of course :)

Bash – Races when piping two commands to a named pipe

Why not just do:

{ echo foo; echo bar;} > /tmp/p

If you want your controlling script to leave the pipe open, you can do:

exec 3<> /tmp/p

Opening a named pipe in read-write mode is to avoid that to block if the pipe hasn't been opened yet. That would instantiate it if it wasn't yet. It works on Linux at least but is not guaranteed to by POSIX.

Alternatively (and portably):

: < /tmp/p & exec 3> /tmp/p

Then instead of having each process open the named pipe, you can also do:

cmd >&3

And in the end, you'd do:

exec 3>&-

To close the writing end to let readers know it's finished.

change all <s to >s and <s to >s if you need the logic to be the other way round.

Best Answer

Related Solutions

Freebsd – How to you get console backgrounds for Arch Linux

Bash – Races when piping two commands to a named pipe

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