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?

/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.

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