[英]Can you help me understand how async await works in Node.js?
我正在尝试在 Node 中为 hubot 编写一个脚本,该脚本在远程服务器上运行命令以获取当前安装在该服务器上的各种第三方软件的当前版本。
我的问题是在我的 getVersions function 快结束时,它调用 getVersionsOverSSH function。 但是,版本数组在尝试打印版本内容之前不会等待被调用的 function 完成。 我在 Node 方面不是很有经验,所以我对 await/async 工作原理的理解是有限的。 有人可以告诉我如何以同步方式运行此脚本,以便在继续之前等待 SSH function 完成吗? 谢谢
获取版本.js
versions = [];
async function getVersions(res) {
const env = getEnvsFromRequest(res.match[2].toString());
const resEnv = resolver.resolveEdiEnv(env);
if (resEnv === null) {
res.reply(`${env} is not in my list of available environments.`);
return;
}
if (resEnv.length > 0) {
response = response.concat(`\nHere are the results for ${resEnv}:\n`);
}
// Resolve hosts for environment
let resHosts = [];
resHosts = await resolver.resolveHosts(resEnv);
// Resolve creds for environment
let resCreds = [];
resCreds = await resolver.resolveCreds(resEnv);
try {
versions = await getVersionsOverSSH(resHosts,resCreds);
console.log(versions) // this line prints before array is loaded
} catch (err) {
console.log(err);
}
}
// function that makes the ssh calls and appends verions into an array
// returns array complete with versions from each command
function getVersionsOverSSH(resHosts,resCreds) {
dummy = [];
const ssh = new SSH({
host: resHosts[1],
user: resCreds[0],
pass: resCreds[1]
});
ssh
// Software 1 version
.exec('head -3 /app/foo/bar | tail -1 | cut -d \'=\' -f 2', {
out(stdout) { dummy.push(`Software 1 version: ${stdout}`); },
})
// Software 2 version
.exec('cd /app/foo/foo/bar && ls -td -- * | head -n 1', {
out(stdout) { dummy.push(`Software 2 version: ${stdout}`); },
})
// Software 3 Version
.exec(`cd /app/foo/bar/foo && ./version.sh | grep Foo* | cut -d \' \' -f 3`, {
out(stdout) { dummy.push(`Software 3: ${stdout}`); },
})
.start();
console.log(dummy); // this prints correctly
return dummy;
}
您需要返回 promise 并在需要时解决。 和 getVersionsOverSSH 里面execSync
function getVersionsOverSSH(resHosts,resCreds) {
return new Promise((resolve, reject) => {
dummy = [];
const ssh = new SSH({
host: resHosts[1],
user: resCreds[0],
pass: resCreds[1]
});
ssh
// Software 1 version
.execSync('head -3 /app/foo/bar | tail -1 | cut -d \'=\' -f 2', {
out(stdout) { dummy.push(`Software 1 version: ${stdout}`); },
})
// Software 2 version
.execSync('cd /app/foo/foo/bar && ls -td -- * | head -n 1', {
out(stdout) { dummy.push(`Software 2 version: ${stdout}`); },
})
// Software 3 Version
.execSync(`cd /app/foo/bar/foo && ./version.sh | grep Foo* | cut -d \' \' -f 3`, {
out(stdout) { dummy.push(`Software 3: ${stdout}`); },
})
.start();
console.log(dummy); // this prints correctly
//
resolve(dummy);
});
}
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