Breakpoint files do not have a single format, and are strictly speaking not self-describing - each program determines what they should contain. thus while some programs expect frequencies, or raw amplitudes, others may expect MIDI numbers or dB; a few (e.g. mixfiles for "submix" etc) allow you to use either amplitude or dB. Many years ago Martin Atkins developed an 'extended" breakpoint file format when creating the Windows GUI program "BrkEdit" (which as I recall runs very nicely under Wine on Linux); this includes the ability to specify logarithmic or exponential spans between points, with a parameter for slope. In the event it has not gained wider currency – Soundloom for example does not use it. Soundloom uses a very complex program "cdparse" behind the scenes to scan any breakpoint file and try to work out which programs would use it, so that they can be enabled in the Process panel.
For modifying breakpoint files (which are mostly space-separated columns of numbers; a few require some text as well) the workhorse program is "columns". Again this it not designed to convert a single value and return the result to stdout unix-style, but to take a breakpoint file as input, split it into single column files if necessary, and generate a new file as necessary. It was also designed (as I note elsewhere) very much for SoundLoom, and may need scripts to be written to drive it comfortably from the command line.
