Try to unbreak the terminal size when working nested

[debarshiray]

When running nested, stty(1) is invoked against the inner
pseudo-terminal pair created by 'podman exec --tty' which may not have
a valid size due to: containers/podman#3946

In such cases, the COLUMNS and LINES variables set by toolbox(1) in the
outer environment should be forwarded.

This should have been part of commit 05544fb.

https://github.com/debarshiray/toolbox/issues/242

[debarshiray]

@tagoh what do you think about this?

[tagoh]

LGTM

As noted, COLUMNS and LINES aren't the exported variables though, it is always synced up when the terminal window size is changed. so the above approach should works as expected on nested.

[debarshiray]

As noted, COLUMNS and LINES aren't the exported variables though,
it is always synced up when the terminal window size is changed. so the
above approach should works as expected on nested.

The issue is that podman exec --tty creates a second pseudo-terminal pair that's nested inside the original pseudo-terminal created by the terminal emulator (eg., GNOME Terminal). This inner PTY is the one that doesn't have a valid size. So we run stty(1) before podman exec --tty to get the size, and then forward it via the variables.

When we invoke toolbox(1) from inside a container (ie., a podman exec --tty session), stty(1) gets run against the inner PTY pair, which might not have a valid size if the terminal window wasn't resized. In that case, the stty(1) output will be invalid, and our only hope is to forward the variables.