On 5/12/2007, at 4:24 PM, L wrote:

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> Question about buttons and knobs..
> What exactly is a knob?
[cut]
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> it simpler. For example the CP command is just a knob for copy..
>

My understanding of knob is an option or a switch.  I guess the  
meaning is like a music console - all those knobs you can turn to  
fiddle with sound.

So you start off with command X that moves bytes from A to B.

So the user does ...

X A B

... and his bytes are moved.

Then dev. "a" adds an option - a knob.

X [a] A B

Then dev. "b" add his option

X [a|b] A B

Then devs "c", "d", "e" etc.  And someone adds the -quiet knob, the - 
verbose knob.  And obviously if you run -quiet you would ignore - 
verbose?  Or the other way round?

X [a|b|c|d|e|f] A B

By now the code starts to have a lot of conditionals:

if a and b but not c
	do this
otherwise if f
	do that

Code gets messy - harder to follow - bugs creep in (potentially  
security related.)  When you want to add feature Z - which ones of  
all those knobs/options should it handle?  In what way?  Was it  
REALLY worth adding all those options for a couple of people here or  
there (who could have piped output / used a Perl script / whatever?)   
Usually not.

I guess it would be the same for an API - you start with a simple  
entry point and end up with a lot of entry points, or having a whole  
heap of options in every entry point.

My 2c ...