[Gambas-user] How to determine the order of magnitude of a Long variable

[Bruce]

I need to determine how many blocks (sectors, writeable chunks, 
whatever) are available on a USB "drive" (stick, sdd, whatever).

I can get a reasonably accurate value Shell'ing the lsblk command. 
However the value could be anywhere between 0 and the total number of 
usable blocks on the device (i.e. the "formatted size").

In order to determine whether the data I am about to write to the device 
will fit I need to know the order of magnitude of these free blocks - 
kB, mB, gB, TB, etc etc.

This is because the utilities that do the writing wont give the size of 
the data in formats other than the so-called "human-readable format" e.g 
3.25G or 4GB or any number of other variants, which may by the way be 
based on 1024 or 1000 byte scales. (Grrr!)

In that first case, that 3.25G could be any number of bytes between (3.0 
gigabytes)+1 and (3.5 gigabytes)-1 but that might not fit onto the drive 
if it tries to write into the "last block on the device".

My goal, in case you are wondering, is to keep the maximum number of 
daily backups as possible on the drive and the Gambas project will be 
run by a cron job (so there is np user interaction).

To be safe I thought I'd take the biggest "about to write" size i.e the 
smalllest scale (I think) convert that to a "Required Blocks" value and 
compare it to the actual AvailableBlocks. This does not work for various 
mathematical reasons. So I need to do it the other way around i.e. is 
the number of AvailableBlocks absolutely larger than the needed blocks.

I have searched the internet for something like this with poor results. 
So in desparation... does anyone have any idea how to get a reliable 
comparison?

tia
bruce