Bash Question: How to get the pid of 2nd terminal tab in 1st terminal tab ?

Lennard37 · 12-04-2021, 05:28 AM

Envirement:
* Linux like Ubuntu, Cinnamon desktop, bash, terminal

How to get to get the pid of 2nd terminal tab in 1st terminal tab ?

Follow sample:

Code:

echo pid $$; gnome-terminal --title="TAB-Titel" --tab --active -- bash -c "echo $$ & echo Hello; read exec bash"

What the sample try to do on this time (dosnt realy work on this time):
* echo the pid of 1st terminal tab on 1st terminal tab
* echo the pid of 2nd terminal tab on 2nd terminal tab

Whats wrong with the sample code?
* I am getting wrong pid as echo on 2nd terminal tab.
* I dont know how to output the pid of 2nd terminal tab on 1st terminal tab also.

Any idea how to do ?

The follow are known:

Its known its possible to get the pid of a terminal by:

Code:

echo $$

Its known its possible to get the pid of a called program by p.e. follow:

Code:

xed & $!

Its known its possible to show the bash used pids by follow:

Code:

ps ax | grep bash

Its known its possible to close terminal Tab by follow for testing purposes:

Code:

kill -15 123456

shruggy · 12-04-2021, 06:21 AM

Quote:

Originally Posted by Lennard37

I am getting wrong pid as echo on 2nd terminal tab.

A quoting issue

Code:

.. -- bash -c "echo $$ & echo Hello; read exec bash"

must be

Code:

.. -- bash -c 'echo $$ & echo Hello; read exec bash'

Lennard37 · 12-04-2021, 07:09 AM

Quote:

Originally Posted by shruggy

A quoting issue
must be

Code:

.. -- bash -c 'echo $$ & echo Hello; read exec bash'

The follow are working great now:

Code:

echo pid $$; gnome-terminal --title="TAB-Titel" --tab --active -- bash -c 'echo $$ & echo Hello; read exec bash'

Now i get the follow:
* echo the pid of 1st terminal tab on 1st terminal tab
* echo the pid of 2nd terminal tab on 2nd terminal tab

THX !!!

Lennard37 · 12-04-2021, 08:53 AM

The follow sample code are doing the follow:
* echo the pid of 1st terminal tab on 1st terminal tab
* echo the pid of 2nd terminal tab on 2nd terminal tab

Copy the follow to the terminal:

Code:

echo pid $$; gnome-terminal --title="TAB-Titel" --tab --active -- bash -c 'echo $$ & echo Hello; read exec bash'

How to output the pid from 2nd terminal tab on 1st terminal tab ?

I tryed the follow on 2nd terminal tab:

Code:

export pid_of_2nd_term_tab=$$

I tryed the follow after than on 1st terminal tab a don't get a output:

Code:

echo $pid_of_2nd_term_tab

Its looks like its not the right way to export a var from one tab to a other.

Any idea to get the pid of 2nd terminal tab available on 1st terminal tab?

boughtonp · 12-04-2021, 11:00 AM

Appears to be a duplicate?

https://www.linuxquestions.org/questions/programming-9/bash-question-how-to-get-the-pid-of-2nd-terminal-tab-in-1st-terminal-tab-4175704469

astrogeek · 12-04-2021, 12:49 PM

Please post your thread in only one forum. Posting a single thread in the most relevant forum will make it easier for members to help you and will keep the discussion in one place. Your two threads have been combined.

NevemTeve · 12-04-2021, 01:19 PM

@OP: Could you please explain what is problem X in your case?

Lennard37 · 12-04-2021, 01:20 PM

Quote:

Originally Posted by boughtonp

Appears to be a duplicate?

https://www.linuxquestions.org/questions/programming-9/bash-question-how-to-get-the-pid-of-2nd-terminal-tab-in-1st-terminal-tab-4175704469

It isn't a duplicate.

boughtonp · 12-04-2021, 03:58 PM

Quote:

Originally Posted by Lennard37

It isn't a duplicate.

Your first post/thread asks:

Quote:

How to get to get the pid of 2nd terminal tab in 1st terminal tab ?

Your second one has:

Quote:

How to output the pid from 2nd terminal tab on 1st terminal tab ?
...
Any idea to get the pid of 2nd terminal tab available on 1st terminal tab?

I don't see the difference?

Also, as NevemTeve suggests - if you still have an outstanding issue - describing what the source problem is (rather than the problem with your attempt to solve it) is likely to get better answers.

Lennard37 · 12-05-2021, 05:29 AM

Quote:

Originally Posted by boughtonp

Your first post/thread asks:

Your second one has:

I don't see the difference?

Also, as NevemTeve suggests - if you still have an outstanding issue - describing what the source problem is (rather than the problem with your attempt to solve it) is likely to get better answers.

Ok. Its looks like I didnt change the headline after splitting the question in two discussion parts.

NevemTeve · 12-05-2021, 11:15 AM

Kindly merge the two parts and explain what your actual problem is.

MadeInGermany · 12-06-2021, 01:17 PM

You can get the parent pid in the child process

Code:

gnome-terminal --title="TAB-Titel" --tab --active -- bash -c 'echo "my pid is $$ and my parent is '$$' !"'

The calling shell concatenates a protected 'string' and $$ and a protected 'string'

With an exported variable everything is accessable in the child process

Code:

export PP=$$
gnome-terminal --title="TAB-Titel" --tab --active -- bash -c 'echo "my pid is $$ and my parent is $PP !"'

Vice versa, getting the pid of the child process, is harder.
You can run the child process in the background and get its pid as $!

Code:

gnome-terminal --title="TAB-Titel" --tab --active -- bash -c 'echo "my pid is $$ and my parent is '$$' !"' &
echo "my pid is $$ and my child was spawned as $! !"

Lennard37 · 12-07-2021, 05:22 AM

Quote:

Originally Posted by MadeInGermany

You can get the parent pid in the child process

One terminal are opening a 2nd terminal tab.
I like to get the pid of 2nd terminal tab on 1st terminal tab.

Thats sounds for me like:
I try to get the child pid available on parent process.

pan64 · 12-07-2021, 05:33 AM

Quote:

Originally Posted by Lennard37

One terminal are opening a 2nd terminal tab.
I like to get the pid of 2nd terminal tab on 1st terminal tab.

Thats sounds for me like:
I try to get the child pid available on parent process.

But unfortunately it is wrong. the tab has no pid. The apps you have are: 1. gnome_terminal, 2. shell in first tab, 3. shell in second tab, ....

When you want to open a new tab you need to "ask" the terminal to do that for you. Every shell will say: the parent process is the gnome-terminal itself.

Lennard37 · 12-07-2021, 05:53 AM

Quote:

Originally Posted by pan64

the tab has no pid.

Its looks for me, every terminal tab have a pid.

Open a terminal and output the pid of current running terminal tabs
pgrep bash

You get a output like

Code:

After than open a additional terminal tab on already opened terminal, p.e by menu item of terminal

Run the follow on 2nd terminal tab and you get the pid of 1st and 2nd terminal tab
pgrep bash

You get a output like

Code:

12345
23456

Now its possible to check the pid of 2nd terminal tab is true or wrong
Kill the process of 2nd terminal tab, pe. by a gui driven process manager, perhaps its possible by kill on terminal to.

So you can see, the the 2nd terminal tab are closing on this way and other terminal tabs dont close on this way. Thats sounds for me, the 2`nd terminal tab have a own pid, which are on this sample is the pid 23456.

So I can do it on follow way:
* Create a list of bash pids after open the terminal (before open the 2nd terminal tab

Code:

arr1=$(pgrep bash)
echo $arr1

* Create a list of bash pids after open the 2nd terminal tab

Code:

arr2=$(pgrep bash)
echo $arr2

* doing a diff of arr1 and arr2, reports me usual the wanted pid

Code:

Thats should work mostly, a have little bit the the risk to get more than one pids as a diff, if other bash terminal are starting at the same small time frame, depend on what ever are running on same system. Thats should be not a big risk. A the risk are bigger than 0. Perhaps, they are a way, without this risk.