Kay•9mo ago

Log output from Deno.ChildProcess while its running

I want to log all output immediately when its logged in the child process. how would i do that?

19 Replies

// Create a new Command that runs the unix command uptime
await new Deno.Command('uptime', {
        stdout: "piped" // Mark the stdout as piped so we can read it
    })
        .spawn() // make a new process
        .output() // wait for the output
        .then(x => new Response(x.stdout).text()) // read the output as a text using the Response object
        .then(console.log); // then print out the text

// Create a new Command that runs the unix command uptime
await new Deno.Command('uptime', {
        stdout: "piped" // Mark the stdout as piped so we can read it
    })
        .spawn() // make a new process
        .output() // wait for the output
        .then(x => new Response(x.stdout).text()) // read the output as a text using the Response object
        .then(console.log); // then print out the text

@Kay here this should help you if you have more questions please let me know if you don't need spawn() then its simpler:

new Deno.Command("uptime")
        .output()
        .then((x) => new Response(x.stdout).text())
        .then(console.log);

new Deno.Command("uptime")
        .output()
        .then((x) => new Response(x.stdout).text())
        .then(console.log);

as with that the stdout is piped by default

KayOP•9mo ago

i do need to spawn it but i dont want to wait for the output. is there a way to get live output from the process?

lucsoft•9mo ago

yes you can use WHATWG Stream for that

KayOP•9mo ago

whats that and how do i implement it?

lucsoft•9mo ago

const process = new Deno.Command("top", { stdout: "piped" }).spawn();

async function reader() {
    const stream = process.stdout
        .pipeThrough(new TextDecoderStream())
    for await (const message of stream) {
        console.log(message);
    }
}

reader(); // not calling await so its "non blocking"

const process = new Deno.Command("top", { stdout: "piped" }).spawn();

async function reader() {
    const stream = process.stdout
        .pipeThrough(new TextDecoderStream())
    for await (const message of stream) {
        console.log(message);
    }
}

reader(); // not calling await so its "non blocking"

you can get the stream of stdout (which itself is a stream) and pipe and modify it. we get raw binary as stream but we want that a string stream so we can print it out or do other stuff with it the deno std also has stream helpers like a csv stream parser or json stream parser when you are parsing multiple lines

KayOP•9mo ago

i did a quick search and stackoverflow said i also could use inherit for the stdout and stderr. whats the difference?

lucsoft•9mo ago

inherit means it uses the same stdout as deno so if you process prints out Hello World deno would print our Hello World

KayOP•9mo ago

yhea the process im running is deno so that should be fine right?

lucsoft•9mo ago

but because its not pipe though "javascript" you itself can't read it

KayOP•9mo ago

ohh

lucsoft•9mo ago

yes, but btw if you subprocess is deno again maybe look into workers typo*

lucsoft•9mo ago

https://docs.deno.com/runtime/manual/runtime/workers there are great docs about it

Workers | Deno Docs

Deno supports

KayOP•9mo ago

yhea im just using Deno.Command to easely generate the command. i want to limit it to only the apis it needs and nothing else and to create a huge list in the deno.json file is a bit cluttered so i wanted to just generate it and store it in a way that can be read and modified better

lucsoft•9mo ago

oh so maybe you want to look into deno tasks?

KayOP•9mo ago

couse im pretty sure there is no other way to specify allows and denies other than in the tasks

lucsoft•9mo ago

you just write deno task stat and it runns the command in the screenshot

KayOP•9mo ago

i did. its just that a huge list of websites in the command is a pain to read and modify

lucsoft•9mo ago

ahh okay i see

KayOP•9mo ago

so id have smth like --allow-net=discord.com,gateway.discord.com,deno.land,0.0.0.0,someotherthing.net and so on

Log output from Deno.ChildProcess while its running

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