$ echo $BASH_VERSION
4.2.25(1)-release

# Just the Major version:
echo $BASH_VERSINFO
4

##</code><code>##

$ bash --version
GNU bash, version 4.2.25(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2011 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

##</code><code>##

GNU bash, version 4.2.25(1)-release (x86_64-pc-linux-gnu)