bashquotesenvironment

How to use an environment variable inside a quoted string in Bash

I've tried various forms of the following in a bash script:

#!/bin/bash
svn diff $@ --diff-cmd /usr/bin/diff -x "-y -w -p -W $COLUMNS"

But I can't get the syntax to correctly expand the COLUMNS environment variable.

I've tried various forms of the following:

svn diff $@ --diff-cmd /usr/bin/diff -x '-y -w -p -W $COLUMNS'

and

svn diff $@ --diff-cmd /usr/bin/diff -x '-y -w -p -W ${COLUMNS}'

and

eval svn diff $@ --diff-cmd /usr/bin/diff -x "-y -w -p -W $COLUMNS"

Suggestions?

Solution

  • If unsure, you might use the 'cols' request on the terminal, and forget COLUMNS:

    COLS=$(tput cols)