The app computes the sum of the exponentials of the two entered integers using an R code. The inputs are passed in the form of a JSON object to the R code via child_process.spawnSync API of node.js.
The app was packaged using electron-packager(v15.2.0) and its structure is as shown in the screenshot below. Source code to reproduce this issue can be obtained from this GitHub folder: https://github.com/wasimaftab/Utils/tree/master/test_js_r_interaction
index.js file contains the code to interact with R. Important note, you need to install rjson R package before attempting to run the electron app as it is used in R to extract the arguments from json object.
In Ubuntu (18.04) the output as expected, see the screenshot below,
The same code fails in Mac (Catalina 10.15.7) after packaging but, works perfectly in development mode, see the screenshot below.
The actual error is as follows:
Error: spawnSync Rscript ENOENT
at Object.spawnSync (internal/child_process.js:1041:20)
at Object.spawnSync (child_process.js:625:24)
at callSync (file:///Users/admin/Desktop/test_js_r_interaction/release-builds-mac/test_js_r_interaction-darwin-x64/test_js_r_interaction.app/Contents/Resources/app.asar/src/index.js:25:23)
at HTMLButtonElement.<anonymous> (file:///Users/admin/Desktop/test_js_r_interaction/release-builds-mac/test_js_r_interaction-darwin-x64/test_js_r_interaction.app/Contents/Resources/app.asar/src/index.js:84:20)
and the js code to interact with R is as follows:
const path = require("path");
const child_process = require('child_process');
const RSCRIPT = 'Rscript';
const defaultOptions = {
verboseResult: false
}
function parseStdout(output) {
try {
output = output.substr(output.indexOf('"{'), output.lastIndexOf('}"'));
return JSON.parse(JSON.parse(output));
} catch (err) {
return err;
}
}
function callSync(script, args, options) {
options = options || defaultOptions;
const result = args ?
child_process.spawnSync(RSCRIPT, [script, JSON.stringify(args)]) :
child_process.spawnSync(RSCRIPT, [script]);
if (result.status == 0) {
const ret = parseStdout(result.stdout.toString());
if (!(ret instanceof Error)) {
if (options.verboseResult) {
return {
pid: result.pid,
result: ret
};
} else {
return ret;
};
} else {
return {
pid: result.pid,
error: ret.message
};
}
} else if (result.status == 1) {
return {
pid: result.pid,
error: result.stderr.toString()
};
} else {
return {
pid: result.pid,
error: result.stderr.toString()
//error: result.stdout.toString()
};
}
}
I will appreciate any suggestion to fix this issue, thanks in advance
The error you're getting, ENOENT, suggests that your OS cannot find Rscript. This can result from the following scenarios:
Rscript is not even installed.
Rscript is installed, but not executable without a "shell". To check whether it is installed, open a Terminal and execute the command as your Electron application would.
If Rscript can be executed from within a Terminal, there could be something wrong with how the installation has set your paths up. There shouldn't be, really, but it might be necessary to execute spawnSync with additional options, such as { shell: true } to get the correct value of PATH.
If Rscript cannot be executed from within a Terminal, forcing Electron to spawn a shell via the above options (which really is what a Terminal does) will not solve this problem. In this case, try to use the complete path to Rscript as the command instead, if you happen to know where it should be installed.
If neither of those solutions help, try reinstalling Rscript altogether and try again. As I can see nothing which would be wrong with your code, I believe it is a problem of installation.
For more information on child_process.spawnSync (command, args, options), see its documentation.
Related
I wrote this little example:
import { isBrowser, isNode } from "browser-or-node";
// runs at load
async function run() {
if (isBrowser) {
document.body.style.backgroundColor = "black";
} else if (isNode) {
const fs = await import("./myLittleScript");
console.log(fs);
}
}
run()
And ./myLittleScript is actually importing the node filesystem module to use if the user runs the script in node.
Is this idea wrong ? What is the right approach ?
I get an error that the script is not found, even though it is in the same directory than the index.ts which is the code pasted here.
This is when bundling it with webpack, but I am interested in knowing whether this is an acceptable approach or not. (I know I could just write 2 functions.)
I have written a NodeJS command-line program with two modes:
mode foo: runs forever until the user presses Ctrl+C
mode bar: runs once
If the user is already running the program in mode foo, then running it again in mode bar will cause errors. Thus, when the user invokes mode bar, I want to search for all other existing copies of my command-line program that are running and kill them (as a mechanism to prevent the errors before they happen).
Getting a list of processes in NodeJS is easy, but that doesn't help me much. If I simply kill all other node processes, then I might be killing other programs that are not mine. So, I need to know which specific node processes are the ones running my app. Is it even possible to interrogate a process to determine that information?
Another option is to have my program write a temporary file to disk, or write a value to the Windows registry, or something along those lines. And then, before my program exists, I could clean up the temporary value. However, this feels like a precarious solution, because if my program crashes, then the flag will never be unset and will remain orphaned forever.
What is the correct solution to this problem? How can I kill my own application?
I was able to solve this problem using PowerShell:
import { execSync } from "child_process";
const CWD = process.cwd();
function validateOtherCopiesNotRunning(verbose: boolean) {
if (process.platform !== "win32") {
return;
}
// From: https://securityboulevard.com/2020/01/get-process-list-with-command-line-arguments/
const stdout = execPowershell(
"Get-WmiObject Win32_Process -Filter \"name = 'node.exe'\" | Select-Object -ExpandProperty CommandLine",
verbose,
);
const lines = stdout.split("\r\n");
const otherCopiesOfMyProgram= lines.filter(
(line) =>
line.includes("node.exe") &&
line.includes("myProgram") &&
// Exclude the current invocation that is doing a 1-time publish
!line.includes("myProgram publish"),
);
if (otherCopiesOfMyProgram.length > 0) {
throw new Error("You must close other copies of this program before publishing.");
}
}
function execPowershell(
command: string,
verbose = false,
cwd = CWD,
): string {
if (verbose) {
console.log(`Executing PowerShell command: ${command}`);
}
let stdout: string;
try {
const buffer = execSync(command, {
shell: "powershell.exe",
cwd,
});
stdout = buffer.toString().trim();
} catch (err) {
throw new Error(`Failed to run PowerShell command "${command}":`, err);
}
if (verbose) {
console.log(`Executed PowerShell command: ${command}`);
}
return stdout;
}
I am trying to setup some automation on a game server for the game Rust.
The game server itself is ran by running its executable file RustDedicated.exe with some arguments.
According to some googling and reading here on Stack Overflow I have made this script:
import config from "config";
import { ChildProcessWithoutNullStreams, spawn } from "child_process";
const GAMESERVERPATH: string = config.get("Environment.RustDedicatedPath");
const EXECUTABLE: string = config.get("Environment.ExecutableFile");
const GAMESERVERARGS: Array<string> = [
"-batchmode",
"+server.port", `${config.get("Server.port")}`,
"+server.level", `"${config.get("Server.level")}"`,
"+server.seed", `${config.get("Server.seed")}`,
"+server.worldsize", `${config.get("Server.worldsize")}`,
"+server.maxplayers", `${config.get("Server.maxplayers")}`,
"+server.hostname", `"${config.get("Server.hostname")}"`,
"+server.description", `"${config.get("Server.description")}"`,
"+server.headerimage", `"${config.get("Server.headerimage")}"`,
"+rcon.port", `${config.get("Rcon.port")}`,
"+rcon.password", `"${config.get("Rcon.password")}"`,
"+rcon.web", `${config.get("Rcon.web")}`
];
const gameServerProc : ChildProcessWithoutNullStreams = spawn(
GAMESERVERPATH+EXECUTABLE,
GAMESERVERARGS,
{
cwd: GAMESERVERPATH,
shell: true,
}
);
gameServerProc.stdout.on("data", (data) => {
console.log(`stdout:${data.toString()}`);
});
gameServerProc.stderr.on("data", (data) => {
console.log(`stderr:${data.toString()}`);
});
gameServerProc.on("error", (err) => {
console.log(`error:${err.message}`);
});
What is happening is that i can see the output of the executable in the terminal window, and the server is firing without errors, but it seems that stdout is not firing the on('data') event.
I never see stdout:.
See the screenshot below where i have Code open, the output is on the bottom right.
Why is my script failing to get the on('data') firing when the executable outputs?
This issue had nothing to do with the code, but rather the game engine Unity. An extra argument -logFile - had to be present for the executable to output to stdout.
const {execSync , exec} = require('child_process')
const res = execSync("help")
console.log(res.toString())
For every command I try to execute (in this case 'help') it throws the error "Error: Command Failed .... not found". What I do not understand?
Dive in NodeJs child process module
I decided to look at NodeJS source code at here to understand the problem. execSync method use spawnSync to run the command, and in the end, it calls checkExecSyncError. In the latter, you can see that if the status code is not 0, it will throw the error "Command failed ...".
Then I try to run const res = spawnSync("help");, and res.status gives me 1. So, the command help actually yields an "invisible" error although we can see the expected output on the terminal.
Note: Exit status 1 is the catch-all for general error, AFAIK. Exit status 0 means success. Further reading
Confirm in the terminal
I go to my terminal to confirm this, I ran help then echo %ERRORLEVEL%. (thank Tim Gilbert) and I received 1. So it totally makes sense for me.
Even the command throws an error, we can still get the output in this case. You can refer to my code below:
const { execSync } = require('child_process')
console.log(process.env.ComSpec);// verify what terminal is used
try {
// success command
const resNpmVersion = execSync("npm -v");
console.log("success", resNpmVersion.toString());
// failed command, the result is printed in the catch block
const resHelp = execSync("HELP");
} catch (error) {
console.log(error.message);
console.log("error", error.stdout.toString());
}
Lesson learned: Check the exit status of the command :)
(I did my test on Windows 10)
I have the following NodeJS code:
var spawn = require('child_process').spawn;
var Unzipper = {
unzip: function(src, dest, callback) {
var self = this;
if (!fs.existsSync(dest)) {
fs.mkdir(dest);
}
var unzip = spawn('unzip', [ src, '-d', dest ]);
unzip.stdout.on('data', function (data) {
self.stdout(data);
});
unzip.stderr.on('data', function (data) {
self.stderr(data);
callback({message: "There was an error executing an unzip process"});
});
unzip.on('close', function() {
callback();
});
}
};
I have a NodeUnit test that executes successfully. Using phpStorm to debug the test the var unzip is assigned correctly
However if I run the same code as part of a web service, the spawn call doesn't return properly and the server crashes on trying to attach an on handler to the nonexistent stdout property of the unzip var.
I've tried running the program outside of phpStorm, however it crashes on the command line as well for the same reason. I'm suspecting it's a permissions issue that the tests don't have to deal with. A web server spawning processes could cause chaos in a production environment, therefore some extra permissions might be needed, but I haven't been able to find (or I've missed) documentation to support my hypothesis.
I'm running v0.10.3 on OSX Snow Leopard (via MacPorts).
Why can't I spawn the child process correctly?
UPDATES
For #jonathan-wiepert
I'm using Prototypical inheritance so when I create an "instance" of Unzipper I set stdout and stderr ie:
var unzipper = Unzipper.spawn({
stdout: function(data) { util.puts(data); },
stderr: function(data) { util.puts(data); }
});
This is similar to the concept of "constructor injection". As for your other points, thanks for the tips.
The error I'm getting is:
project/src/Unzipper.js:15
unzip.stdout.on('data', function (data) {
^
TypeError: Cannot call method 'on' of undefined
As per my debugging screenshots, the object that is returned from the spawn call is different under different circumstances. My test passes (it checks that a ZIP can be unzipped correctly) so the problem occurs when running this code as a web service.
The problem was that the spawn method created on the Object prototype (see this article on Protypical inheritance) was causing the child_process.spawn function to be replaced, so the wrong function was being called.
I saved child_process.spawn into a property on the Unzipper "class" before it gets clobbered and use that property instead.