On 27/10/2025 20:29, Chet Ramey wrote:
This is the part I don't get. It's not bash that sets the shell to raw
mode, since there's not a tty in the mix, so it must be something in how
it's invoked, or another program that sets the terminal modes and then
execs bash.
In my setup when invoking `ssh -q -o ControlPath=none -tt -o
"RemoteCommand=bin/sh -i" <host>` seems to be creating a tty and that
tty is also set to canonical mode. If I then feed it two nested shells
it looses output. A simple example of this is:
```
/bin/sh --noediting -i
/bin/sh --noediting -c 'cat -'
Lorem ipsum ...
```
Then some amount of the sent data which should be printed by the `cat`
gets lost. Throwing in some `stty`'s here and there seems to reveal that
the tty does actually remain in canonical mode when the subshells are
invoked, so I'm actually a bit confused why there are problems here.
I did also place an `strace -e read,ioctl` on the first subshell, and it
essentially shows two consecutive lines:
```
ioctl(255, TCGETS, {opost isig icanon echo ...}) = 0
read(0, "/bin/sh --noediting -c 'cat -'\nLorem ipsum...", 128) = 128
```
Based on this it seems like the middle shell is performing the
read-ahead. It also seems like the TTY should probably be in the correct
state. Though I'm not entirely sure if the fd `255` corresponds to the
right one. It could also be an issue with the pseudo-terminal allocated
by ssh.
Removing the middle shell also makes the problem go away.
I will need to do some more poking around. I'd welcome any other ideas
for things to try.
Thanks,
Rudi
