available memory

[David J Bell]

Does anyone know of a function, intrinsic to UNIX, or not, that 
will return the currently-available amount of memory that may
be alloc'ed. I understand that this number would not be guaranteed
for any length of time, especially in a multi-user system. I 
really need to use it to instrument a program that is gobbling 
inordinate amounts of RAM, in library function for which I do 
not have the source...

Thanks, 

Dave