Purpose
With no arguments, show the name of the currently selected red
filter. With one argument, set the red filter to the named
position.
Usage
filterr [name [focus]]
Arguments
name = name of the new filter to select
focus = new red 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 red filter
filterr
2) change the red filter to "R"
filterr R
3) change the red filter to "B" and set focus to 2000
filterr B 2000