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

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."

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.