####Shell Variables
$ echo $SHELL # environment variable
/bin/bash
$ echo $PATH # most powerful shell variable, where unix looks for files
$ echo $PS1 # gives what my prompt is
reshama$ # host name
$ export PS1='' # this sets prompt to blank
# colorize prompt
$ export PS1='\e[0;34m\ \h:\W \u\$
34 = blue
30 = black