| -a | display all variables | 
 
 | -b | print value without new line | 
 
 | -e | ignore unknown variables errors | 
 
 | -N | print variable names without values | 
 
 | -n | print only values of the given variable(s) | 
 
 | -p FILE | read values from file | 
 
 | --system | read values from all system directories | 
 
 | -r PATTERN | select setting that match expression | 
 
 | -q | do not echo variable set | 
 
 | -w | enable writing a value to variable | 
 
 | -h | display help and exit | 
 
 | -V | output version information and exit |