I would like to run in subshell some script and redirect it into
another script. Something like this:

my_first_script 2>&1 | my_second_script &

But I also want to save the PID of process of "my_first_script" for
future use.
I know that in bash, I can use $! variable to save the PID. But, of
course, after previous command the $! contains PID of
"my_second_script", not "my_first_script" which I want.

Any suggestions how to solve it?
Thanks for all hints

On Mar 13, 3:18 pm, Teni <t...@volny.cz> wrote:
> I would like to run in subshell some script and redirect it into
> another script. Something like this:
>
> my_first_script 2>&1 | my_second_script &
>
> But I also want to save the PID of process of "my_first_script" for
> future use.
> I know that in bash, I can use $! variable to save the PID. But, of
> course, after previous command the $! contains PID of
> "my_second_script", not "my_first_script" which I want.
>
> Any suggestions how to solve it?
> Thanks for all hints

I have a cheap cheat, not really an ingenious solution:
Since my_first_script is a shell script, it can always retrieve $$
from it and save it in a file, and can be retrieved later

On 13 Bøe, 13:43, Jeenu <jee...@gmail.com> wrote:
> On Mar 13, 3:18 pm, Teni <t...@volny.cz> wrote:
>
> > I would like to run in subshell some script and redirect it into
> > another script. Something like this:
>
> > my_first_script 2>&1 | my_second_script &
>
> > But I also want to save the PID of process of "my_first_script" for
> > future use.
> > I know that in bash, I can use $! variable to save the PID. But, of
> > course, after previous command the $! contains PID of
> > "my_second_script", not "my_first_script" which I want.
>
> > Any suggestions how to solve it?
> > Thanks for all hints
>
> I have a cheap cheat, not really an ingenious solution:
> Since my_first_script is a shell script, it can always retrieve $$
> from it and save it in a file, and can be retrieved later

Well, generally, "my_first_script" can also by a program, I need some
general-purpose solution...
But thank You anyway, good idea although it is not usable for my
purpose.

Any other ideas?

Teni wrote:

> I would like to run in subshell some script and redirect it into
> another script. Something like this:
>
> my_first_script 2>&1 | my_second_script &
>
> But I also want to save the PID of process of "my_first_script" for
> future use.
> I know that in bash, I can use $! variable to save the PID. But, of
> course, after previous command the $! contains PID of
> "my_second_script", not "my_first_script" which I want.
>
> Any suggestions how to solve it?
> Thanks for all hints

A (not so) dirty trick might be this:

$ ps | grep my_first_script

and go from there to extract the PID with the usual tools.

On 13 Bøe, 14:26, pk <p...@pk.pk> wrote:
> Teni wrote:
> > I would like to run in subshell some script and redirect it into
> > another script. Something like this:
>
> > my_first_script 2>&1 | my_second_script &
>
> > But I also want to save the PID of process of "my_first_script" for
> > future use.
> > I know that in bash, I can use $! variable to save the PID. But, of
> > course, after previous command the $! contains PID of
> > "my_second_script", not "my_first_script" which I want.
>
> > Any suggestions how to solve it?
> > Thanks for all hints
>
> A (not so) dirty trick might be this:
>
> $ ps | grep my_first_script
>
> and go from there to extract the PID with the usual tools.

Well,
fine trick but there may be quite a lot of "my_first_script" running
in a system so it can be a bit complicated to recognize which one is
the right one...

I think that there should be some way how to run the "my_first_script"
then read the PID ($!) then run "my_second_script" and somehow shuffle
the file-descriptors to redirect stdout and stderr from
"my_first_script" to "my_second_script". I am currently searching for
such a solution but stil dont have it since i am not a shell-guru...

Teni wrote:

>> A (not so) dirty trick might be this:
>>
>> $ ps | grep my_first_script
>>
>> and go from there to extract the PID with the usual tools.
>
> Well,
> fine trick but there may be quite a lot of "my_first_script" running
> in a system so it can be a bit complicated to recognize which one is
> the right one...

If you make certain assumptions (which of course might not be true) things
could be a bit easier. For example, if you know the PID of the shell or
process that started the thing, so you could do something eg

$ ps --ppid $$ | grep my_first_script

to restrict the results (replace $$ with the pid of the parent). Of course,
this will be still useless if many "my_first_script"s have the same parent
shell (or parent process, for that matter).

But you might be correct in that this is probably not a good way to go.

2008-03-13, 03:18(-07), Teni:
> I would like to run in subshell some script and redirect it into
> another script. Something like this:
>
> my_first_script 2>&1 | my_second_script &
>
> But I also want to save the PID of process of "my_first_script" for
> future use.
> I know that in bash, I can use $! variable to save the PID. But, of
> course, after previous command the $! contains PID of
> "my_second_script", not "my_first_script" which I want.
[...]

{
pid=$(
exec 3>&1 >&-
sh -c 'echo "$$" >&3
exec 3>&-
exec my_first_script' 2>&1 |
my_second_script 3>&- >&4 &
)
} 4>&1

--
Stéphane

On 13 Bøe, 16:58, pk <p...@pk.pk> wrote:
> Teni wrote:
> >> A (not so) dirty trick might be this:
>
> >> $ ps | grep my_first_script
>
> >> and go from there to extract the PID with the usual tools.
>
> > Well,
> > fine trick but there may be quite a lot of "my_first_script" running
> > in a system so it can be a bit complicated to recognize which one is
> > the right one...
>
> If you make certain assumptions (which of course might not be true) things
> could be a bit easier. For example, if you know the PID of the shell or
> process that started the thing, so you could do something eg
>
> $ ps --ppid $$ | grep my_first_script
>
> to restrict the results (replace $$ with the pid of the parent). Of course,
> this will be still useless if many "my_first_script"s have the same parent
> shell (or parent process, for that matter).
>
> But you might be correct in that this is probably not a good way to go.

That assumption is always true in my case, so thank You, this is good
enough for me and pretty simple.
Teni