Question

我想将子进程的stdout / stderr流式传输到文件和父进程。

说我有这个：

const cp = require('child_process');
const fs = require('fs');

const fd = fs.openSync('bar.log','a');

const child = cp.spawn('node', [ 'foo.js' ], {
  cwd: __dirname,
  stdio: [ 'ignore', fd, fd ]
});

// using stdio array above I send stdout/stderr to log file
// but I would still like to receive stdout/stderr to this process so I can do something else with it

child.stdout.setEncoding('utf8');
child.stderr.setEncoding('utf8');

child.stdout.on('data', function (d) {
  console.log('stdout => ', d);
});

child.stderr.on('data', function (d) {
  console.log('stderr => ', d);
});

如果你运行它，它会给我这个错误：

child.stdout.setEncoding('utf8');
            ^

TypeError: Cannot read property 'setEncoding' of null
    at Object.<anonymous> (/Users/Olegzandr/WebstormProjects/oresoftware/suman/private/exp9.js:14:13)
    at Module._compile (module.js:541:32)
    at Object.Module._extensions..js (module.js:550:10)
    at Module.load (module.js:458:32)
    at tryModuleLoad (module.js:417:12)
    at Function.Module._load (module.js:409:3)
    at Module.runMain (module.js:575:10)
    at run (node.js:348:7)
    at startup (node.js:140:9)
    at node.js:463:3

它的含义是，如果没有为stdout或stderr选择'pipe'，那么该子进程的stdout / stderr将不会被传递给父进程。因此没有定义child.stdout和child.stderr ......

但是如果我想将stdout / stderr传递给父文件和文件呢？

我必须这样做：

const cp = require('child_process');
const fs = require('fs');

const child = cp.spawn('node', [ 'foo.js' ], {
  cwd: __dirname,
  stdio: [ 'ignore', 'pipe', 'pipe' ]
});

// using stdio array above I send stdout/stderr to log file
// but I would still like to receive stdout/stderr to this process so I can do something else with it

child.stdout.setEncoding('utf8');
child.stderr.setEncoding('utf8');

const strm = fs.createWriteStream('bar.log');

child.stdout.pipe(strm);   //new code
child.stderr.pipe(strm);   //new code

child.stdout.on('data', function (d) {
  console.log('stdout => ', d);
});

child.stderr.on('data', function (d) {
  console.log('stderr => ', d);
});

或者还有另一种方法可以做到这一点我还没见过？

管道stdio到文件和父进程

0 个答案: