LINES and COLUMNS environmental variables lost in a script

Question

Consider the following:

me@mine:~$ cat a.sh 
#!/bin/bash
echo "Lines: " $LINES
echo "Columns: " $COLUMNS
me@mine:~$ ./a.sh 
Lines: 
Columns: 
me@mine:~$ echo "Lines: " $LINES
Lines:  52
me@mine:~$ echo "Columns: " $COLUMNS
Columns:  157
me@mine:~$

The variables $LINES and $COLUMNS are shell variables, not environmental variables, and thus are not exported to the child process (but they are automatically updated when I resize the xterm window, even when logged in via ssh from a remote location). Is there a way in which I can let my script know the current terminal size?

EDIT: I need this as a workaround do this problem: vi (as well as vim, less, and similar commands) messes up the screen every time I use it. Changing the terminal is not an option, and thus I'm looking for workarounds (scrolling down $LINES lines surely is not the perfect solution, but at least is better than losing the previous screen)

Answer 1

Have you tried making your shebang say:

#!/bin/bash -i

Answer 2

You could get the lines and columns from tput

#!/bin/bash

lines=$(tput lines)
columns=$(tput cols)

echo "Lines: " $lines
echo "Columns: " $columns

Answer 3

$LINES and $COLUMNS in bash is just a shell-y wrapper around the TTY ioctls giving you the size of the TTY and the signals sent by the terminal every time that size changes.

You could write a program in some other language which calls those ioctls directly to get to the TTY dimensions, and then use that program.

EDIT: Well, turns out that program already exists, and is called tput. Vote up Puppe's tput based answer.