> +if ( diff --version < /dev/null 2>&1 | grep GNU ) 2>&1 > /dev/null;
> then
> + compare() { diff -u "$@"; }'diff -u' is required by POSIX 2008. Rather than filtering on whether 'diff --version' includes GNU, it would be better to filter on whether 'diff -u' is accepted on the command line, to allow other POSIX-compliant implementations their chance. Something like 'diff -u /dev/null /dev/null' giving no output and having a 0 status should be a sufficient filter. -- Eric Blake
