Re: read with redirected stdin

[Pier Paolo Grassi <pierpaolog@gmail.com>]

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Thanks, I'll check it out.

Il giorno dom 8 gen 2023 alle 05:29 Jim <linux.tech.guy@gmail.com> ha
scritto:

>
> On Sat, Jan 7, 2023 at 11:23 AM Pier Paolo Grassi <pierpaolog@gmail.com>
> wrote:
>
>> Thanks, but i don't _always_ redirect stdin.
>> i wonder how is ps getting the tty (it displays an ? when there is no tty
>> for the process)
>> I suppose it uses /proc, but couldn't find a reference or the info
>> exploring the /proc fs by myself.
>> for now I am asking directly ps:
>> [[ "$(ps h -o tty $$)" != "?" ]] && ...
>>
>> Pier Paolo Grassi
>>
>> Hi,
>
> Don't really have an answer how ps gets its info but the attached script
> is something
> I have been working on. It uses the /proc file system directly to get
> info. It uses zstat
> to look for the tty info.  If nothing is returned it substitutes '?".
> Some processes point to
> /dev/null. The script is still a work in progress. I was trying to get the
> same results as
> "ps -eHo uid=,pid=,ppid=,tty=,comm=" via a zsh script.
>
> This doesn't answer your original question, but may give you some insight
> into the
> /proc file system.
>
> Hope the script is helpful.
>
> Regards,
>
> Jim Murphy
>
> --
Pier Paolo Grassi

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