Node.js physical cpu count

// Source of https://www.npmjs.com/package/physical-cpu-count

'use strict'

const os = require('os')
const childProcess = require('child_process')

function exec (command) {
  const output = childProcess.execSync(command, {encoding: 'utf8'})
  return output
}

let amount
const platform = os.platform()

if (platform === 'linux') {
  const output = exec('lscpu -p | egrep -v "^#" | sort -u -t, -k 2,4 | wc -l')
  amount = parseInt(output.trim(), 10)
} else if (platform === 'darwin') {
  const output = exec('sysctl -n hw.physicalcpu_max')
  amount = parseInt(output.trim(), 10)
} else if (platform === 'windows') {
  const output = exec('WMIC CPU Get NumberOfCores')
  amount = output.split(os.EOL)
    .map(function parse (line) { return parseInt(line) })
    .filter(function numbers (value) { return !isNaN(value) })
    .reduce(function add (sum, number) { return sum + number }, 0)
} else {
  const cores = os.cpus().filter(function (cpu, index) {
    const hasHyperthreading = cpu.model.includes('Intel')
    const isOdd = index % 2 === 1
    return !hasHyperthreading || isOdd
  })
  amount = cores.length
}

module.exports = amount

In a simpler way, with Node JS : os.cpus()

Returns an array of objects containing information about each CPU/core installed: model, speed (in MHz), and times (an object containing the number of milliseconds the CPU/core spent in: user, nice, sys, idle, and irq).

The length of this array is the number of "processors" in the system. Most systems only have one CPU, so that's the number of cores of that CPU.

os.cpus() is not the same thing - it will return the logical cores, and the code above gives you physical cores. If you have an Intel CPU with hyperthreading enabled, and have 4 physical cores, os.cpus().length will be 8, but you actually have 4 physical cores. If you want 8 for some reason, os.cpus() will give you what you want but if you want 4 (most likely what you want) then you need the above code.

I think this is not working for my AMD Ryzen 7 1800x. I'm still getting 16 instead of 8

That's because os.platform() returns 'win32' for windows and not 'windows' as here. Check my fork for proper solution.

I am getting 'win32' for windows, so it falls back to the cpus(). I changed it to else if (platform === 'windows' || platform === 'win32') {

Node 18.14.0 and newer support os.availableParallelism() which should be used instead of os.cpus().length, this still only returns the number of logical processors, not the number of physical processors.