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Re: read with redirected stdin

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

Il giorno sab 7 gen 2023 alle ore 14:44 Roman Perepelitsa <roman.perepelitsa@xxxxxxxxx> ha scritto:
On Sat, Jan 7, 2023 at 2:32 PM Pier Paolo Grassi <pierpaolog@xxxxxxxxx> wrote:
> Hello, I have a script that asks to create a target dir if it doesn't exist.
> to that extend I inserted an
> read -k1
> in the script.
> To be able to ask the user for confirm even when the script stdin is connected to a pipe I did
> read -k1 < /dev/tty

Note that this redirect doesn't affect `read -k1`. It'll read from the
terminal either way.

You can do something like this in your script:

  if [[ -r $TTY ]]; then
    read -k1
    read -k1 -u0

There is a corner case when you log in as root and then su to a
non-privileged user. $TTY won't be readable even though the process
has a TTY. Since you are redirecting stdin anyway, this corner case
shouldn't affect you.


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