Determine if an executable (or library) is 32 or 64 bit

Is it possible to get information about any binary on OS X to determine if it's a 32 bit or 64 bit binary?

I played with the 'otool' c开发者_C百科ommand but can't find this kind of information.

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Use the file command instead of otool. It will list all the architectures in the binary. On Intel Macs i386 is 32 bit and x86_64 is 64 bit.

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From Nicholas in a comment, lipo -info also works. This is what you must use on static libraries, since file only displays "current ar archive random library."