Distinguish Terminals

Eilya · 09-21-2008, 01:45 AM

Hi dear friends,

I want to know how can we distinguish between 2 terminals. if I am int terminal 1 (/dev/pts/1) then I want to $echo "Hello" in /dev/pts/2, how can I do it?

Regards,
Eilya

Bolsak · 09-21-2008, 01:52 AM

I think you can just do it anyway, like if I am on tty1 and I want to say"Hello" to tty2, I just put

Code:

echo "Hello" > /dev/tty2

Mr. C. · 09-21-2008, 02:07 AM

How about setting your prompt such that it includes the TTY? Example:

Code:

$ PS1='\l $ '
ttyp0 $ 
$ tty
/dev/ttyp0
ttyp0 $

The \l is the tty name in bash prompts. There are other escapes you can include. See PROMPTING in man bash.

Eilya · 09-21-2008, 02:48 AM

Thank you Bolsak,

Quote:

How about setting your prompt such that it includes the TTY? Example:

Code:

PS1='\l $ '
$ PS1='\l $ '
ttyp0 $
$ tty
/dev/ttyp0
ttyp0 $

The \l is the tty name in bash prompts..

Please explain this code, I can not believe this

Mr. C. · 09-21-2008, 02:58 AM

# set the bash prompt to be the tty name followed by a $
$ PS1='\l $ '

Now we see the prompt appears to be set to the tty name followed by $
ttyp0 $

Let's check with the tty command:
$ tty
/dev/ttyp0

Yes, indeed, we are on ttyp0

ttyp0 $

and this is our prompt again.

Edit: The previous code was copy/pasted from different shell sessions. Here's another example:

Code:

$ pwd
/usr/bin
$ PS1='[\h:\w] @ \l $ '
[glacier:/usr/bin] @ ttyp0 $ tty
/dev/ttyp0
[glacier:/usr/bin] @ ttyp0 $ PS1='$ '
$ tty
/dev/ttyp0

Eilya · 09-21-2008, 03:22 AM

Thanks Mr.C, about that code

Quote:

echo "Hello" > /dev/tty2

can we include users in it? I mean if we want to send message to another user, what should we do??

Thanks,
Eilya

Mr. C. · 09-21-2008, 03:33 AM

What you are doing is something different. You are sending the output of the echo command via redirection onto the named terminal device. This just blasts characters to the device, without formatting or concern for what is currently on the screen. This is like what the write command does.

If you want to send messages, refer to the Chat thread you have open here: http://www.linuxquestions.org/questi...system-671335/

Eilya · 09-21-2008, 11:10 AM

I have a question: I want to have a code like this:

Quote:

echo "hello" > /dev/pts/6

when I am in terminal 1 (/dev/pts/1), I want to just choose the terminal number, so When

Quote:

$a=6

the some how I want to have :

Quote:

$b=/dev/pts/$a

what should I do to have the paths includes: /dev/pts/
or for some distros: /dev/tty
how can I choose this paths????

Regards,
Eilya

Eilya · 09-21-2008, 01:03 PM

any ideaaaaaaaaaa?

Mr. C. · 09-21-2008, 02:14 PM

Do something like:

ttypathbase='/dev/pts'
a=6

echo hello > $ttypathbase/$a

and change ttypathbase in your .bashrc or .bash_profile based on distribution.

I'm not sure ultimately what you want to accomplish, so its hard to give you a more comprehensive solution.

Eilya · 09-21-2008, 06:50 PM

Thanks Mr.C, so we can not use the path and just edit the number?? for example we can have the terminal path by:

Quote:

a=$tty

and it returns something like /dev/pts/1 or /dev/ttyp0 now if we could have tty command and then edit just the numbers, for example: /dev/pts/$a or /dev/ttyp$a , it could be more compatible with any distro. can we do anything for it??????

Regards,
Eilya

Mr. C. · 09-21-2008, 07:26 PM

You can create a function:

Code:

function ttypath {
    distro=$(uname -s)
    case $distro in
        Linux*)
            echo /dev/tty$1 ;;
        NetBSD*)
            echo /dev/tty0$1 ;;
        *)
            echo UNKNOWN ;;
    esac
}

which you call by:

Code:

$ ./ttypath 2
/dev/tty02

But beware, there are problems. There are different both TTYs and PTYs, and they have different naming conventions:

Code:

$ ls -l /dev/tty0 /dev/ptya0 
crw-rw-rw- 1 root tty 2, 176 Aug 16  2007 /dev/ptya0
crw--w---- 1 root tty 4,   0 Aug 16  2007 /dev/tty0

So you'll have to modify the function above to suit your needs and tty types, but this should give you the idea.

Eilya · 09-22-2008, 02:35 AM

Thanks a lot, Mr.C, As I understood there is no way for making a simple and optimum way for knowing and using the terminal path in different distros.

Thanks a lot,
Eilya