I used to do this with omxplayer before, on Raspberry Pi, and it worked fine:
const ChildProcess = require("child_process");
ChildProcess.exec(command, function (err) {
if (err !== null) {
console.log("" + err);
}
});
I could pass any omxplayer-related arguments within the command string, without issues.
With VLC on the other hand, executing cvlc [pathToAudioFile] doesn't do anything.
Oh, and I tried the exact same command, i.e. using the same file path, from the CLI and it played the audio file perfectly.
So how do I start VLC (using cvlc) from within NodeJS and pass arguments to it as well?
The reason that the cvlc [pathToFile] command didn't produce an outcome was incorrect permissions on the media file. chmod-ing that file with 777 solved the problem.
Related
I have a node js application which needs to access ffmpeg. My approach to this has been to use {exec} from the child_processes module built into Node. The problem is that {exec} always starts the cmd line from the current directory and I can't figure out how to point the directory context to where ffmpeg.exe is located so that I can access the program. Is my approach flawed? How can I access a seperate CLI application from Node?
This code returns "'ffmpeg' is not recognized as an internal or external command" because I'm obviously in Node's execution context which is not where ffmpeg is located.
I also do not want to store the node application in the directory of ffmpeg.exe because that's just lazy and impractical.
exec(`ffmpeg -i ${filepathToMedia} --vf fps=1 ${outputdirectory}/out%d.png`, (error, stdout, stderr) => {
if (error) {
console.log(`error: ${error.message}`);
return;
}
if (stderr) {
console.log(`stderr: ${stderr}`);
return;
}
if(stdout) {
console.log(`success: ${stdout}`)
} });
You could do one of two things here:
Use the absolute path to the ffmpeg executable so instead of just exec('ffmpeg ...') you'd do something likeexec('C:\Users\user\ffmpeg_dir\ffmpeg ...') This isn't very clean and will probably break if someone else tries to use your code.
Add your ffmpeg directory to your system's PATH environment variable. If you add ffmpeg to your PATH it becomes available as ffmpeg regardless of what folder you're in, allowing the script to work as-is. This'll also make it easier for other people to run your script.
I am trying to run MacOS shortcuts via NodeJS script. To achieve that I created shortcuts in the MacOS Shortcuts app, which normally run in the terminal (ZSH) by typing shortcuts run shortcutname (Docs). They work fine when typing them directly into the terminal, but not when called from a NodeJS script.
My script looks like this:
exec('shortcuts run shortcutname', (error, stdout, stderr) => {
if (error) {
console.log(`error: ${error.message}`);
return;
}
if (stderr) {
console.log(`stderr: ${stderr}`);
return;
}
console.log(`stdout: ${stdout}`);
});
When starting the script from the terminal node script.js it does nothing. It does not return anything nor does it finish. I tried replacing the command shortcuts run shortcutname by other commands the system should know. For example ls, or git. They all work. Also when I leave out the shortcutname in the end, it complains about the missing parameter.
I was suspecting missing access rights, but apparently NodeJS runs as my normal user. Running whoami in script context returns my user name.
NODE_DEBUG=cluster,net,http,fs,tls,module,timers node script.js did not show anything unusual. I also tried using the full path of the binary. which shortcuts gave me /usr/bin/shortcuts. Which I used in my script /usr/bin/shortcuts run shortcutname.
What am I missing? Thanks in advance!
Though I thought I tested it, I found the solution:
execSync instead of exec works
It’d be cool if someone could explain why exec wouldn’t work.
Cheers!
I'm facing a very odd issue where I have a Node script which invokes a process, it looks like this:
// wslPath declared here (it's a shell file)
const proc = cp.spawn('ubuntu.exe', ['run', wslPath]);
let stdout = '';
proc.stdout.on('data', data => stdout += data.toString());
let stderr = '';
proc.stderr.on('data', data => stderr += data.toString());
return await new Promise((resolve, reject) => {
proc.on('exit', async code => {
await fs.remove(winPath);
if (code) {
reject({ code, stdout, stderr });
}
resolve({ stdout, stderr });
});
});
As you can see, the script invokes WSL. WSL is enabled on the computer. When I run this script manually, it works fine. When I log in to the computer the script is at using RDP from another computer and run it with the same credentials, it works fine as well. But when the script is invoked from a scheduled task which also runs with the same credentials, the spawn call returns:
(node:4684) UnhandledPromiseRejectionWarning: Error: spawn UNKNOWN
at ChildProcess.spawn (internal/child_process.js:394:11)
at Object.spawn (child_process.js:540:9)
I verified the user is the same by logging require('os').userInfo() and require('child_process').spawnSync('whoami', { encoding: 'utf8' }) and it returns the same in all three cases.
I assume it is because ubuntu.exe is not being found, but I don't know why that would be as the user is the same in all three cases.
What could be the reason for this and how can I debug this further?
The Windows Task Scheduler allows you to specify a user to run as (for privilege reasons), but does not give you the environment (PATH and other environment variables) that are configured for that user.
So, when running programs from the Windows Task Scheduler, it's important to not make any assumptions about what's in the environment (particularly the PATH). If my program depends on certain things in the environment, I will sometimes change my Task to be a .BAT file that first sets up the environment as needed and then launch my program from there.
Among other things, the simplest way to not rely on the path is to specify the full path to the executable you are running rather than assuming it will be found in the path somewhere. But, you also need to make sure that your executable can find any other resources it might need without any environment variables or you need to configure those environment variables for it before running.
I'm trying to make this little QoL app that can trigger my scripts inside package.json of any project I throw at it (react, polymer, etc.).
So far, it works as it should. At least until I kill the app or want to terminate the specific process (like using ctrl+c while running a npm start in a console).
I'm currently calling the command this way:
const exec = require("child_process").execFile;
...
let ps = exec("command.bat", [path, command], (error, stdout, stderr)=>{}) //command.bat contains only: cd "%1" \n npm "%2"
Previously I've used node-powershell like so:
const Shell = require('node-powershell');
...
let sh = new Shell();
sh.addCommand(`cd ${fs.realpathSync(path)}`);
sh.addCommand(`npm ${command}`);
sh.invoke();
And I've already tried using ps-tree in hopes that this will list all the processes started by my process so I can kill them but no luck and because it creates additional process or two it's getting out of hands really quickly.
const cp = require('child_process');
...
psTree(ps.pid, function (err, children) {
cp.spawn('kill', ['-9'].concat(children.map(function (p) { return p.PID })));
});
So if there is some solution I would be really grateful. I'm also open to any different solution if there is any.
Thanks in advance.
I've got some experience with Ruby and Rake, but now I'm working on a Node project and want to learn how to do the same things with Jake.
Ruby has a system function that will shell out to a command and wait for it to exit. Rake extends this by adding an sh function that will additionally throw an error if the child process returned a nonzero exit code (or couldn't be found at all). sh is really handy for Rake tasks that shell out to things like compilers or test frameworks, because it automatically terminates the task as soon as anything fails.
Node doesn't seem to have anything like system or sh -- it looks like the nearest equivalents are child_process.spawn and child_process.exec, but neither of them wires up STDOUT or STDERR, so you can't see any output from the child process unless you do some extra work.
What's the best way to get an sh method for Jake? (Though since this is Node, I'd expect it to be async, rather than blocking until the command returns like Ruby does.) Is there an npm module that has already invented this particular wheel, or does someone have a code sample that does this?
I've already seen sh.js, but it looks awfully heavyweight for this (it tries to build an entire command interpreter in Node), and it doesn't look like it's async (though the docs don't say one way or the other).
I'm looking for something that I could use more or less like this (using Jake's support for async tasks):
file('myprogram', ['in.c'], function() {
// sh(command, args, successCallback)
sh('gcc', ['in.c', '-o', 'myprogram'], function() {
// sh should throw if gcc couldn't be found or returned nonzero.
// So if we got here, we can tell Jake our task completed successfully.
complete();
});
}, true);
Here's some code I've come up with that seems to work well. (But if anyone has a better answer, or knows of an existing npm module that already does this, please add another answer.)
Supports full shell syntax, so you can use | and < and > to pipe and redirect output, you can run Windows batch files, etc.
Displays output (both STDOUT and STDERR) as the child process generates it, so you see incremental output as the command runs.
No limitation on the amount of output the command can generate (unlike a previous exec-based version of this code).
Cross-platform (works on Windows, should work on Mac/Linux as well). I borrowed the platform-specific-shell (if platform === 'win32') technique from npm.
Here's the code:
function sh(command, callback) {
var shell = '/bin/sh', args = ['-c', commandLine], child;
if (process.platform === 'win32') {
shell = 'cmd';
args = ['/c', commandLine];
}
child = child_process.spawn(shell, args);
child.stdout.pipe(process.stdout);
child.stderr.pipe(process.stderr);
child.on('exit', function(code, signal) {
if (signal != null)
throw new Error("Process terminated with signal " + signal);
if (code !== 0)
throw new Error("Process exited with error code " + code);
callback();
});
};