Collin Funk wrote:
> Section 8.3 "Other Environment Variables" has a decent description [1].
> The newest draft is better since it mentions tcgetwinsize & tcsetwinsize.
>
> The process goes something like:
>
> 1. If $LINES and $COLUMNS are set to positive decimal numbers use them.
> - POSIX recommends users leave these unset unless there is a reason
> to override system behavior (e.g. output narrower than the actual
> window).
Here's the first thinko. Many programs (ps, pstree, man/groff) are supposed
to write their output through a pager program, e.g. 'less'. Which means that
the program does not write to a terminal; it writes to a pipe. If COLUMNS
is unset in this situation, the POSIX recommentation will not match user
expectations:
* Through $TERM and the terminal description, resized terminal windows
in a GUI don't work:
$ infocmp -L xterm | grep columns
columns#80, init_tabs#8, lines#24, max_colors#8,
* tcgetwinsize does not work either, since it works only on ttys, not
on pipes.
The result would be that when a pager program is used, column widths are
nearly always wrong.
> ...
> I think bash updates $LINES and $COLUMNS after every command by default,
> but I'm not sure how other shells behave.
It would be useful to test this with a few more shells, to see whether
it can be relied upon.
Bruno
