如何调试Node.js中stdout的意外输出问题？

DevOps 小满

2026-7-27

控制台输出异常缩进问题

相关代码如下：

console.log('A');
console.log('B');
console.log('C');

预期输出应为：

A
B
C

但实际输出却是：

A
 B
  C

这段代码位于一个包含其他逻辑的大型应用中。

我猜测是应用的其他部分向process.stdout写入了空白字符，但尝试捕获所有write调用后，并未找到问题根源：

const traces = [];

const originalStdout = process.stdout.write.bind(process.stdout);

process.stdout.write = (message) => {
    originalStdout(message);
    
    traces.push({
        message,
        stack: new Error().stack,
    });
};

const originalStderr = process.stderr.write.bind(process.stderr);

process.stderr.write = (message) => {
    originalStderr(message);
    
    traces.push({
        message,
        stack: new Error().stack,
    });
};

process.on('SIGINT', () => {
    console.error(traces);
});

生成的输出为：

A
 B
  C
   ^C[
  {
    message: 'A\n',
    stack: 'Error\n' +
      '    at process.stdout.write (/Users/gajus/Developer/contra/gaia/node_modules/.pnpm/turbowatch@2.16.3/node_modules/turbowatch/dist/bin/turbowatch.js:31:16)\n' +
      '    at console.value (node:internal/console/constructor:299:16)\n' +
      '    at console.log (node:internal/console/constructor:376:26)\n' +
      '    at flush (/Users/gajus/Developer/contra/gaia/node_modules/.pnpm/turbowatch@2.16.3/node_modules/turbowatch/dist/createSpawn.js:43:15)\n' +
      '    at output.noLeading (/Users/gajus/Developer/contra/gaia/node_modules/.pnpm/turbowatch@2.16.3/node_modules/turbowatch/dist/createSpawn.js:59:5)\n' +
      '    at Timeout.exec [as _onTimeout] (/Users/gajus/Developer/contra/gaia/node_modules/.pnpm/throttle-debounce@5.0.0/node_modules/throttle-debounce/cjs/index.js:85:16)\n' +
      '    at listOnTimeout (node:internal/timers:573:17)\n' +
      '    at process.processTimers (node:internal/timers:514:7)'
  },
  {
    message: 'B\n',
    stack: 'Error\n' +
      '    at process.stdout.write (/Users/gajus/Developer/contra/gaia/node_modules/.pnpm/turbowatch@2.16.3/node_modules/turbowatch/dist/bin/turbowatch.js:31:16)\n' +
      '    at console.value (node:internal/console/constructor:299:16)\n' +
      '    at console.log (node:internal/console/constructor:376:26)\n' +
      '    at flush (/Users/gajus/Developer/contra/gaia/node_modules/.pnpm/turbowatch@2.16.3/node_modules/turbowatch/dist/createSpawn.js:45:15)\n' +
      '    at output.noLeading (/Users/gajus/Developer/contra/gaia/node_modules/.pnpm/turbowatch@2.16.3/node_modules/turbowatch/dist/createSpawn.js:59:5)\n' +
      '    at Timeout.exec [as _onTimeout] (/Users/gajus/Developer/contra/gaia/node_modules/.pnpm/throttle-debounce@5.0.0/node_modules/throttle-debounce/cjs/index.js:85:16)\n' +
      '    at listOnTimeout (node:internal/timers:573:17)\n' +
      '    at process.processTimers (node:internal/timers:514:7)'
  },
  {
    message: 'C\n',
    stack: 'Error\n' +
      '    at process.stdout.write (/Users/gajus/Developer/contra/gaia/node_modules/.pnpm/turbowatch@2.16.3/node_modules/turbowatch/dist/bin/turbowatch.js:31:16)\n' +
      '    at console.value (node:internal/console/constructor:299:16)\n' +
      '    at console.log (node:internal/console/constructor:376:26)\n' +
      '    at flush (/Users/gajus/Developer/contra/gaia/node_modules/.pnpm/turbowatch@2.16.3/node_modules/turbowatch/dist/createSpawn.js:46:15)\n' +
      '    at output.noLeading (/Users/gajus/Developer/contra/gaia/node_modules/.pnpm/turbowatch@2.16.3/node_modules/turbowatch/dist/createSpawn.js:59:5)\n' +
      '    at Timeout.exec [as _onTimeout] (/Users/gajus/Developer/contra/gaia/node_modules/.pnpm/throttle-debounce@5.0.0/node_modules/throttle-debounce/cjs/index.js:85:16)\n' +
      '    at listOnTimeout (node:internal/timers:573:17)\n' +
      '    at process.processTimers (node:internal/timers:514:7)'
  }
]

为了验证，我尝试了多个Node.js版本和不同终端，但输出均一致。

更奇怪的是，执行以下代码时：

process.stdout.write('A');
process.stdout.write('B');
process.stdout.write('C');

输出为：

ABC

这符合预期——但结合之前console.log的表现，我原本以为会出现空白字符。

这种异常并非一直发生，应该是后台运行的某些程序造成的干扰。我通过在脚本顶部添加定时console.log验证了这一点：

setInterval(() => {
    console.log('|');
}, 10);

脚本输出如下：

看起来有程序在向stdout注入空白字符。但改用process.stdout.write执行相同逻辑时，却没有出现空白字符🤯：

setInterval(() => {
    process.stdout.write('|');
}, 10);

输出：

||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

更诡异的是，如果在这段代码中添加换行符，就又会出现异常行为：

setInterval(() => {
    process.stdout.write('|\n');
}, 10);

输出：

我还尝试重写stdout和stderr，确保只写入.\n：

const originalStdout = process.stdout.write.bind(process.stdout);

process.stdout.write = (message) => {
    originalStdout('.\n');
};

const originalStderr = process.stderr.write.bind(process.stderr);

process.stderr.write = (message) => {
    originalStderr('.\n')
};

结果依然出现相同的异常：

我认为有必要说明，该脚本的其他部分使用了child_process.spawn()，这应该和问题有关。

内容的提问来源于stack exchange，提问作者Gajus