Purpose
With no arguments, show the name of the currently selected blue
filter. With one argument, set the blue filter to the named
position.
Usage
filterb [name [focus]]
Arguments
name = name of the new filter to select
focus = new blue focus value or "auto" for autofocus
Output
The name of the current or new filter is printed to stdout
Restrictions
"name" must be a valid filter name
Exit values
0 = normal completion
1 = wrong number of arguments
2 = autofocus not yet implemented
Example
1) show the current blue filter
filterb
2) change the blue filter to "R"
filterb R
3) change the blue filter to "B" and set focus to 2000
filterb B 2000