monitor screen output

monitor screen output

[Ray Andrews]

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All:

Can zsh monitor screen output in a backgroundy sort of way?  Say I have 
several programs that might at some time or other output some message, 
can zsh keep an eye on the screen any time it is written to and detect 
that message and act upon it?

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Re: monitor screen output

[Bart Schaefer]

On Mon, Nov 11, 2024 at 8:45 AM Ray Andrews <rayandrews@eastlink.ca> wrote:
>
> Can zsh monitor screen output in a backgroundy sort of way?

No.  That would need to be a function of the terminal itself (or
terminal emulator, which might have a better chance).

Otherwise if you direct those messages to a file, there are various
ways (still not directly part of zsh) to monitor file changes.

Re: monitor screen output

[Ray Andrews]

On 2024-11-11 08:49, Bart Schaefer wrote:
> On Mon, Nov 11, 2024 at 8:45 AM Ray Andrews <rayandrews@eastlink.ca> wrote:
>> Can zsh monitor screen output in a backgroundy sort of way?
> No.  That would need to be a function of the terminal itself (or
> terminal emulator, which might have a better chance).
>
> Otherwise if you direct those messages to a file, there are various
> ways (still not directly part of zsh) to monitor file changes.
I think the terminal emulator I use does keep a file.  I'll look into 
that.  It would be cool if every screen write tripped a flag somewhere 
tho, then it would be easy.  Tx.


>

Re: monitor screen output

[Eric Pruitt]

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On Mon, Nov 11, 2024 at 09:18:31AM -0800, Ray Andrews wrote:
> I think the terminal emulator I use does keep a file.  I'll look into that. 
> It would be cool if every screen write tripped a flag somewhere tho, then it
> would be easy.  Tx.

Depending on what exactly you want to do, you could probably achieve
this using tmux and some combination of its hooks, pane flags and/or
pipe-pane. I recommend searching for "monitor-", "-hook" and "pipe-pane"
in tmux(1). Whether this would be better than Expect would depend on the
task at hand. If you don't already use tmux and aren't interested in
using it, Expect is probably better.

Eric

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Re: monitor screen output

[Ray Andrews]

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On 2024-11-11 10:13, Eric Pruitt wrote:
> Depending on what exactly you want to do, you could probably achieve 
> this using tmux and some combination of its hooks, pane flags and/or 
> pipe-pane. I recommend searching for "monitor-", "-hook" and 
> "pipe-pane" in tmux(1). Whether this would be better than Expect would 
> depend on the task at hand. If you don't already use tmux and aren't 
> interested in using it, Expect is probably better.
>
> Eric
>
Thanks.  I tried to decipher tmux once and got nowhere, it's one of 
those situations where the documentation presumes you are already adept 
with the thing.  I'll take another look tho.




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Re: monitor screen output

[Josef Sachs]

>>>>> On Mon, 11 Nov 2024 08:49:37 -0800, Bart Schaefer said:

> On Mon, Nov 11, 2024 at 8:45 AM Ray Andrews <rayandrews@eastlink.ca>
> wrote:
>> 
>> Can zsh monitor screen output in a backgroundy sort of way?

> No.  That would need to be a function of the terminal itself (or
> terminal emulator, which might have a better chance).

> Otherwise if you direct those messages to a file, there are various
> ways (still not directly part of zsh) to monitor file changes.

Perhaps consider expect. The Wikipedia page also lists some alternatives.
https://en.wikipedia.org/wiki/Expect

Re: monitor screen output

[Ray Andrews]

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On 2024-11-11 09:24, Josef Sachs wrote:
> Perhaps consider expect. The Wikipedia page also lists some alternatives.
> https://en.wikipedia.org/wiki/Expect
>
That looks like exactly the thing.  Thanks Josef.

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Re: monitor screen output

[Sebastian Stark]

Am Montag, den 11. November 2024 um 17:45 schrieb Ray Andrews:
>All:
>
>Can zsh monitor screen output in a backgroundy sort of way?  Say I 
>have several programs that might at some time or other output some 
>message, can zsh keep an eye on the screen any time it is written to 
>and detect that message and act upon it?

If you want it to be done natively in zsh you could probably use the 
zpty module (see zshmodules(1)):

Load the module:

   $ zmodload zsh/zpty

Start top in the background. That would be your program to monitor.
It will get the handle 'top'. You may start several programs with 
different handles:

   $ zpty top top

Read from the pseudo terminal into "var" until pattern "*mutt*" was 
found:

   $ zpty -r top var "*neomutt*"

Now Start neomutt in another shell. Above command should return after a 
couple seconds and $var should contain the top output including the 
matched text.

Cancel the background process if you are done:

   $ zpty -d top


Expect is probably the saner option to use.


Sebastian

Re: monitor screen output

[Ray Andrews]

On 2024-11-11 13:35, Sebastian Stark wrote:
>
> Load the module:
>
>   $ zmodload zsh/zpty
>
Never heard of it.  Sounds interesting tho, I'll take a look.