In a subshell, how to read an environment variable from the calling shell?

Question

For the obvious reason I do not want to export COLUMNS in my normal bash shell.

However for the purpose of one particular subshell, I need access to the value of COLUMNS of its parent. In other words, in a regular bash shell, I want to call a shell script that uses ls -Cw $COLUMNS, with the value of $COLUMNS from its parent.

Is there any way to access a parent's environment variables other than them being exported by the parent?

Answer 1

You can't. But there are ways to get the number of columns other than environment variables. For example

COLUMNS=$(tput cols)