Why is /usr/bin/arch not installed?

My application has been depending on the presence of /usr/bin/arch, and it was my understanding that 开发者_JAVA百科this was part of the standard Mac OS X installation. It's there if I install Snow Leopard from the DVD, without installing the developer tools. However, I've now encountered two users with 10.6.7 who are missing this file. Is there a normal way of getting Mac OS X that omits arch? Or do these users' installations just happen to be broken?

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/usr/bin/arch is part of the com.apple.pkg.BaseSystem package, so it should be present in every stock Mac OS X installation. Running:

$ pkgutil --file-info /usr/bin/arch

will tell you the package that installed /usr/bin/arch, and running:

$ pkgutil --files com.apple.pkg.BaseSystem

will tell you the contents of that package.

It might be worth it to run the latter in the machines of those users that haven’t got arch.

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I'm not sure why this file would be missing, but uname -p prints the processor architecture name. Check man uname for other variables.