Bash command substitution not working as expected

Question

I'd like to view the last few lines of a file, but I want the columns aligned. Basically, I want to disable wordwrap.

This is straightforward with:

tail $FILE | cut -c -80

But I'm trying to generalize my script for other users, and I'd like to cut to the actual terminal width, which I can get with:

stty size | cut -d" " -f2

So I would imagine that I could just

tail $FILE | cut -c -`stty size | cut -d" " -f2`

but it doesn't work:

stty: standard input: Invalid argument
cut: invalid range with no endpoint: -
Try `cut --help' for more information.

(Same results with the 'new' $() expansion.)

Now, if I echo it, it seems fine:

echo cut -c -`stty size | cut -d" " -f2`
cut -c -103

Am I just missing an escape char? Or is this somehow just not possible?

Thanks.

Answer 1

The reason that it doesn't work is because stty is executed within a pipe. Therefore it doesn't "see" the underlying terminal. In your script you could store the terminal width in a variable like

size=`stty size | cut -d" " -f2`

and then use that next:

tail $FILE | cut -c -$size

Answer 2

Bash maintains the screen width in the COLUMNS variable, which you can use in a pipeline:

tail $FILE | cut -c -$COLUMNS