How to get the amount of free virtual memory on Apple / Mac?

How do I get the amount of free virtual memory on Mac OSX?

I'm speaking of total free virtual memory (or: free addresses) and also the biggest allocatable continou开发者_JAVA技巧s block of memory available for the current process.

(Like e.g. on Windows returned by GlobalMemoryStatus (free mem) or querieable with a combination of GetSystemInfo / VirtualQuery (biggest block))

EDIT: this is to monitor the memory fragmentation and be alerted of areas or situations, where this gets really bad. Targeting (also) 32 bit.

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In short, you can't. Mostly because it isn't a useful number as it changes all the time and, for 64 bit applications, if you tried to use a many GB (or many TB) allocation, you'd swap to death anyway.

What are you trying to do?