您必须通过将其输送到两个流中来创建流的副本。您可以使用PassThrough流创建简单流，只需将输入传递到输出即可。
const spawn = require('child_process').spawn;
const PassThrough = require('stream').PassThrough;
const a = spawn('echo', ['hi user']);
const b = new PassThrough();
const c = new PassThrough();
a.stdout.pipe(b);
a.stdout.pipe(c);
let count = 0;
b.on('data', function (chunk) {
count += chunk.length;
});
b.on('end', function () {
console.log(count);
c.pipe(process.stdout);
});
输出：
8
hi user
602392714
清零编程群