command substitution function BASH programming introduction bash functions command substitution http://www.tldp.org/HOWTO/Bash-Prog-Intro-HOWTO-8.html bash functions tldp.org/HOWTO/Bash-Prog-Intro-HOWTO-8.html#ss8.2 http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO-8.html bash functions command substitution