To determine if OS X is running on a 64-bit box, Homebrew uses:
/usr/sbin/sysctl hw.cpu64bit_capable
We also figure out if we're 10.5 or 10.6 with:
/usr/bin/sw_vers -productVersion
Many of our brews then switch to 64-bit mode if we're on 10.6 (or later) and 64-bit capable, otherwise, on 10.5 or a Core Duo we switch to 32-bit mode.
To determine if OS X is running on a 64-bit box, Homebrew uses:
/usr/sbin/sysctl hw.cpu64bit_capable
We also figure out if we're 10.5 or 10.6 with:
/usr/bin/sw_vers -productVersion
Many of our brews then switch to 64-bit mode if we're on 10.6 (or later) and 64-bit capable, otherwise, on 10.5 or a Core Duo we switch to 32-bit mode.