cpu

Read current CPU usage and system uptime.

import { cpu } from "system";

Availability

Available in the Main script only.

Table of Contents

• Methods
• Practical Examples

Methods

cpu.usage() #

cpu

Returns the current total CPU usage across all cores as a percentage. Calculated from the delta between consecutive calls using GetSystemTimes.

First call always returns 0

The usage calculation requires two measurements to compute a delta. The very first call to cpu.usage() always returns 0.0 because no baseline has been established yet. Subsequent calls return the actual usage measured since the previous call.

RETURNS: number CPU usage as a floating-point percentage in the range 0.0–100.0. Returns 0.0 if stats are unavailable or on the very first call.

import { cpu } from "system";

// First call establishes the baseline — returns 0
cpu.usage();

// Poll every second for real readings
setInterval(() => {
  const usage = cpu.usage();
  ipcMain.send("cpu-update", { cpu: Math.round(usage) });
}, 1000);

cpu.getUpTime([format]) #

cpu

Returns system uptime since the last boot. Without a format string the raw value is a floating-point number of seconds. With a format string the tokens are replaced with the corresponding time components.

Format tokens:

Token	Description	Example
%d	Days (not zero-padded)	3
%h	Hours within the day (not zero-padded)	4
%m	Minutes within the hour (not zero-padded)	9
%s	Seconds within the minute (not zero-padded)	7
%H	Hours, zero-padded to 2 digits	04
%M	Minutes, zero-padded to 2 digits	09
%S	Seconds, zero-padded to 2 digits	07

Default format

When getUpTime is called with an empty string "", the default format "%d days, %h hours, %m minutes" is used.

PARAMETERS

format string OPTIONAL

Format string using the tokens listed below. If omitted, returns total uptime in seconds as a float.

RETURNS: number | string | null Total uptime in seconds as a number when no format is given, a formatted string when a format is provided, or null if uptime cannot be read.

import { cpu } from "system";

// Raw seconds (floating point)
const seconds = cpu.getUpTime();
console.log("Uptime seconds:", seconds); // e.g. 259331.234

// Formatted string
const uptime = cpu.getUpTime("%d days, %H:%M:%S");
console.log("Uptime:", uptime); // e.g. "3 days, 04:02:11"

// Using unpadded tokens
const brief = cpu.getUpTime("%d d %h h %m m");
console.log(brief); // e.g. "3 d 4 h 2 m"

// Default format (pass empty string)
const def = cpu.getUpTime("");
console.log(def); // e.g. "3 days, 4 hours, 2 minutes"

Practical Examples

Live CPU bar updated every second

import { cpu } from "system";

// Warm up the baseline on startup
cpu.usage();

setInterval(() => {
  const usage = cpu.usage();
  ipcMain.send("stats", { cpu: Math.round(usage) });
}, 1000);

Display uptime in the widget

import { cpu } from "system";

setInterval(() => {
  const uptime = cpu.getUpTime("%d days, %H:%M:%S");
  ipcMain.send("uptime-update", { text: uptime });
}, 1000);

CPU usage with history graph

import { cpu } from "system";

const history = [];
const MAX_POINTS = 60;

// Establish baseline
cpu.usage();

setInterval(() => {
  const usage = cpu.usage();
  history.push(Math.round(usage));
  if (history.length > MAX_POINTS) history.shift();

  ipcMain.send("cpu-history", { usage, history });
}, 1000);