[skizziepop]

nproc isn't available on some of the BSDs

[sigjuice]

  $ nproc 
  ksh: nproc: not found
  $ uname -a
  OpenBSD obsd64.example.xyz 6.8 GENERIC.MP#828 arm64
  $ sysctl hw.ncpu                                                               
  hw.ncpu=2

[oso2k]

Right. So on Mac or other BSDs, you want use a ‘sysctl’.

[floatingatoll]

On Macs, this "total cores available" strategy might not be a valid approach, since you probably only want to be using the high-performance cores and not also the low-power ones — and the CPU might well overbook all your threads to high-perf to leave room for the OS and other programs, even if you try to do otherwise.

[oso2k]

Another thought, I don’t know if Alpine Linux or other musl-libc based systems will have ‘nproc’ if, for instance, you’re running containers or other minimal systems.

[toast0]

cpuset -g on FreeBSD >= 7.1 will tell you what cpus are available to your shell, where a sysctl will only tell you what's on your system. (Lots of good info in the related manual pages)