nodejs 在函数中等待 exec

Question

我喜欢在一个自定义函数中集成 nodejs 的 exec 来处理这个函数中的所有错误。

const exec = require('child_process').exec;

function os_func() {
    this.execCommand = function(cmd) {
        var ret;
        exec(cmd, (error, stdout, stderr) => {
            if (error) {
                console.error(`exec error: ${error}`);
                return;
            }
            ret = stdout;
        });
        return ret;
    }
}
var os = new os_func();

此函数 returns 未定义，因为当值 returns 时 exec 尚未完成。我该如何解决？我可以强制函数等待 exec 吗？

Answer 1

由于命令是异步执行的，因此您需要使用 callback 在命令执行完毕后处理 return 值：

const exec = require('child_process').exec;

function os_func() {
    this.execCommand = function(cmd, callback) {
        exec(cmd, (error, stdout, stderr) => {
            if (error) {
                console.error(`exec error: ${error}`);
                return;
            }

            callback(stdout);
        });
    }
}
var os = new os_func();

os.execCommand('SomeCommand', function (returnvalue) {
    // Here you can get the return value
});

Answer 2

exec 将以异步方式处理它，因此您应该收到回调或 return 承诺。

为了使其同步，您可以做的一件事是改用 execSync：

https://nodejs.org/api/child_process.html#child_process_child_process_execsync_command_options

The child_process.execSync() method is generally identical to child_process.exec() with the exception that the method will not return until the child process has fully closed. When a timeout has been encountered and killSignal is sent, the method won't return until the process has completely exited. Note that if the child process intercepts and handles the SIGTERM signal and doesn't exit, the parent process will wait until the child process has exited.

Answer 3

您可以将 promise 用作：

const exec = require('child_process').exec;

function os_func() {
    this.execCommand = function (cmd) {
        return new Promise((resolve, reject)=> {
           exec(cmd, (error, stdout, stderr) => {
             if (error) {
                reject(error);
                return;
            }
            resolve(stdout)
           });
       })
   }
}
var os = new os_func();

os.execCommand('pwd').then(res=> {
    console.log("os >>>", res);
}).catch(err=> {
    console.log("os >>>", err);
})

Answer 4

你可以通过回调来完成。也许你可以尝试这样的事情：

function os_func() {
this.execCommand = function(cmd, myCallback) {
    var ret;
    exec(cmd, (error, stdout, stderr) => {
        if (error) {
            console.error(`exec error: ${error}`);
            return;
        }
        ret = stdout;
        myCallback(ret);

    });
}


function myCallback(ret){
      // TODO: your stuff with return value...
}

Answer 5

另一种使用 ES6 模块的解决方案：

import fs from "node:fs";
import {exec} from "node:child_process";
import util from "node:util";

// promisify exec
const execPromise = util.promisify(exec);

try {
  // wait for exec to complete
  const {stdout, stderr} = await execPromise("ls -l");
} catch (error) {
  console.log(error);
}

Answer 6

添加对我有用的内容，因为上面的 none 成功了！

const { exec } = require("child_process");
const util  = require("util");
const execPromise = util.promisify(exec);

function parentFunction() {
...
  // Trigger 'exec', then a-wait for it to finish
  await execWrapper('<your-command-here>');
...
}

...
async function execWrapper(cmd) {
  const { stdout, stderr } = await execPromise(cmd);
  if (stdout) {
    console.log(`stderr: ${stdout}`);
  }
  if (stderr) {
    console.log(`stderr: ${stderr}`);
  }
}

注意：这不是您的示例，只是一个通用示例；对我来说 - cmd 是一个 Docker build 命令。如果需要，您可能 execWrapper return 支持 stdout。

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