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Re: read with redirected stdin

Thanks, I'll check it out.

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

On Sat, Jan 7, 2023 at 11:23 AM Pier Paolo Grassi <pierpaolog@xxxxxxxxx> 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

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.


Jim Murphy

Pier Paolo Grassi

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