@netlify/build/lib/plugins/child/systemLog.js

Netlify build module

import { appendFileSync, openSync } from 'fs';
import { inspect } from 'util';
const systemLogLocation = '/dev/fd/4';
export const getSystemLog = () => {
    try {
        // throws if system log wasn't hooked up
        const fd = openSync(systemLogLocation, 'a');
        return (message) => {
            const stringifiedMessage = typeof message === 'string' ? message : inspect(message);
            appendFileSync(fd, `${stringifiedMessage}\n`);
        };
    }
    catch {
        // not accessible
    }
};