Capturing exit code from python in JS via cmd child process - javascript

So I have python script called main.py
#!/usr/bin/env python3
print("hello")
exit (12)
I am trying to capture the exit code via nodejs
const cp = require('child_process');
cp.exec('python main.py', (er, stdout, stderr) => {
console.log(stdout)
}).on('close', (code) => {
console.log(code)
});
This works and outputs "hello" and "12". But I need to execute python script via another cmd unit. I have tried the code below
const cp = require('child_process');
cp.exec('start cmd /k python ./main.py', (er, stdout, stderr) => {
console.log(stdout)
}).on('close', (code) => {
console.log(code)
});
But this outputs "hello" and "0" instead of "12". I have been trying to figure this out for past couple hours but not getting anywhere. What am I missing here?
Calling a another child process is not solution for me, since I am also trying to run the python script on a development unit instead on cmd

Related

How to run bash commands from Node.js and get result

I want to run a bash script on my server using a Node js function and get the result back in Node through a callback. Sample script is as follows -
grep -c "eventName" 111data.csv
Is this possible? I looked at the following module but looks very complex. Does anyone know of a way this can be done?
https://www.npmjs.com/package/bashjs
You can execute a command
const { exec } = require('child_process');
const grep = exec('grep -c "eventName" 111data.csv', function (error, stdout, stderr) {
if (error) {
console.log(error.stack);
console.log('Error code: '+error.code);
console.log('Signal received: '+error.signal);
}
console.log('Child Process STDOUT: '+stdout);
console.log('Child Process STDERR: '+stderr);
});
grep.on('exit', function (code) {
console.log('Child process exited with exit code '+code);
});
Just modified the example from the Node.js article. Didn't actually test it

how to execute js script file as child process node.js

I have a problem, I'm trying to execute file that sending mail using nodemailer and I need to execute it from another JS file I tried to do it like this:
const exec = require('child_process').exec;
exec('"C:/Users/NikitaSeliverstov/node_modules/.bin/send.js"');
but mail is not sending. I don't need to send params the file send.js just sending text file with fully specified path . Sorry for obvious question but I can't figure it out.
Also I tried to do it like this:
const exec = require('child_process').exec;
exec('"node C:/Users/NikitaSeliverstov/node_modules/.bin/send.js"');
you need to specify a callback function which will be called after your exec command is executed:
i created 2 files:
anotherTest.js
console.log('another test');
test.js
const exec = require('child_process').exec;
const child = exec('node anotherTest.js',
(error, stdout, stderr) => {
console.log(`stdout: ${stdout}`);
console.log(`stderr: ${stderr}`);
if (error !== null) {
console.log(`exec error: ${error}`);
}
});
this is the output:
stdout: another test
stderr:
you run the test.js script by doing "node test.js" in the terminal/console. you can change the arguments of the exec command with the arguments that you want.

How to run windows cmd.exe commands from javascript code run on node bash?

Is there a way where I can invoke a windows batch file from inside the javascript code? Or any other healthy way to do the below through any node package?
scripts.bat
ECHO "JAVASCRIPT is AWESOME"
PAUSE
scripts.js
// Code to read and run the batch file //
On the command prompt:
C:/> node scripts.js
One way to do this is with child_process. You just have to pass the file you want to execute.
const execFile = require('child_process').execFile;
const child = execFile('scripts.bat', [], (error, stdout, stderr) => {
if (error) {
throw error;
}
console.log(stdout);
});

Pipe a javascript variable into shell command with nodejs

I'm working on a nodejs application and I need to pipe a multi-line string into a shell command. I'm not a pro at shell scripting but if I run this command in my terminal it works just fine:
$((cat $filePath) | dayone new)
Here's what I've got for the nodejs side. The dayone command does work but there is nothing piped into it.
const cp = require('child_process');
const terminal = cp.spawn('bash');
var multiLineVariable = 'Multi\nline\nstring';
terminal.stdin.write('mul');
cp.exec('dayone new', (error, stdout, stderr) => {
console.log(error, stdout, stderr);
});
terminal.stdin.end();
Thanks for any help!
Here, you're starting up bash using spawn, but then you're using exec to start your dayone program. They are separate child processes and aren't connected in any way.
'cp' is just a reference to the child_process module, and spawn and exec are just two different ways of starting child processes.
You could use bash and write your dayone command to stdin in order to invoke dayone (as your snippet seems to be trying to do), or you could just invoke dayone directly with exec (bear in mind exec still runs the command in a shell):
var multiLineVariable = 'Multi\nline\nstring';
// get the child_process module
const cp = require('child_process');
// open a child process
var process = cp.exec('dayone new', (error, stdout, stderr) => {
console.log(error, stdout, stderr);
});
// write your multiline variable to the child process
process.stdin.write(multiLineVariable);
process.stdin.end();
With Readable Streams it's really easy to listen to the input
const chunks = [];
process.stdin.on('readable', () => {
const chunk = process.stdin.read()
chunks.push(chunk);
if (chunk !== null) {
const result = Buffer.concat(chunks);
console.log(result.toString());
}
});
With Writable Streams you can write to the stdout
process.stdout.write('Multi\nline\nstring');
Hopefully I could help you

How to execute shell command in Javascript

I want to write a JavaScript function which will execute the system shell commands (ls for example) and return the value.
How do I achieve this?
I'll answer assuming that when the asker said "Shell Script" he meant a Node.js backend JavaScript. Possibly using commander.js to use frame your code :)
You could use the child_process module from node's API. I pasted the example code below.
var exec = require('child_process').exec;
exec('cat *.js bad_file | wc -l',
function (error, stdout, stderr) {
console.log('stdout: ' + stdout);
console.log('stderr: ' + stderr);
if (error !== null) {
console.log('exec error: ' + error);
}
});
I don't know why the previous answers gave all sorts of complicated solutions. If you just want to execute a quick command like ls, you don't need async/await or callbacks or anything. Here's all you need - execSync:
const execSync = require('child_process').execSync;
// import { execSync } from 'child_process'; // replace ^ if using ES modules
const output = execSync('ls', { encoding: 'utf-8' }); // the default is 'buffer'
console.log('Output was:\n', output);
For error handling, add a try/catch block around the statement.
If you're running a command that takes a long time to complete, then yes, look at the asynchronous exec function.
...few year later...
ES6 has been accepted as a standard and ES7 is around the corner so it deserves updated answer. We'll use ES6+async/await with nodejs+babel as an example, prerequisites are:
nodejs with npm
babel
Your example foo.js file may look like:
import { exec } from 'child_process';
/**
* Execute simple shell command (async wrapper).
* #param {String} cmd
* #return {Object} { stdout: String, stderr: String }
*/
async function sh(cmd) {
return new Promise(function (resolve, reject) {
exec(cmd, (err, stdout, stderr) => {
if (err) {
reject(err);
} else {
resolve({ stdout, stderr });
}
});
});
}
async function main() {
let { stdout } = await sh('ls');
for (let line of stdout.split('\n')) {
console.log(`ls: ${line}`);
}
}
main();
Make sure you have babel:
npm i babel-cli -g
Install latest preset:
npm i babel-preset-latest
Run it via:
babel-node --presets latest foo.js
This depends entirely on the JavaScript environment. Please elaborate.
For example, in Windows Scripting, you do things like:
var shell = WScript.CreateObject("WScript.Shell");
shell.Run("command here");
In a nutshell:
// Instantiate the Shell object and invoke its execute method.
var oShell = new ActiveXObject("Shell.Application");
var commandtoRun = "C:\\Winnt\\Notepad.exe";
if (inputparms != "") {
var commandParms = document.Form1.filename.value;
}
// Invoke the execute method.
oShell.ShellExecute(commandtoRun, commandParms, "", "open", "1");
Note: These answers are from a browser based client to a Unix based web server.
Run command on client
You essentially can't. Security says only run within a browser and its access to commands and filesystem is limited.
Run ls on server
You can use an AJAX call to retrieve a dynamic page passing in your parameters via a GET.
Be aware that this also opens up a security risk as you would have to do something to ensure that mrs rouge hacker does not get your application to say run: /dev/null && rm -rf / ......
So in a nutshel, running from JS is just a bad, bad idea.... YMMV
With NodeJS is simple like that!
And if you want to run this script at each boot of your server, you can have a look on the forever-service application!
var exec = require('child_process').exec;
exec('php main.php', function (error, stdOut, stdErr) {
// do what you want!
});
function exec(cmd, handler = function(error, stdout, stderr){console.log(stdout);if(error !== null){console.log(stderr)}})
{
const childfork = require('child_process');
return childfork.exec(cmd, handler);
}
This function can be easily used like:
exec('echo test');
//output:
//test
exec('echo test', function(err, stdout){console.log(stdout+stdout+stdout)});
//output:
//testtesttest
Here is simple command that executes ifconfig shell command of Linux
var process = require('child_process');
process.exec('ifconfig',function (err,stdout,stderr) {
if (err) {
console.log("\n"+stderr);
} else {
console.log(stdout);
}
});
If you are using npm you can use the shelljs package
To install: npm install [-g] shelljs
var shell = require('shelljs');
shell.ls('*.js').forEach(function (file) {
// do something
});
See more: https://www.npmjs.com/package/shelljs
Another post on this topic with a nice jQuery/Ajax/PHP solution:
shell scripting and jQuery
In IE, you can do this :
var shell = new ActiveXObject("WScript.Shell");
shell.run("cmd /c dir & pause");
With nashorn you can write a script like this:
$EXEC('find -type f');
var files = $OUT.split('\n');
files.forEach(...
...
and run it:
jjs -scripting each_file.js
As far as I can tell, there is no built-in function, method or otherwise, in the official ECMAScript specification to run an external process. That said, extensions are allowed, see this note from the spec, for example:
NOTE Examples of built-in functions include parseInt and Math.exp. A
host or implementation may provide additional built-in functions that
are not described in this specification.
One such "host" is Node.js which has the child_process module. Let's try this code to execute the Linux shell command ps -aux, saved in runps.js, based on the child_process documentation:
const { spawn } = require('child_process');
const ps = spawn('ps', ['-aux']);
ps.stdout.on('data', (data) => {
console.log(`stdout: ${data}`);
});
ps.stderr.on('data', (data) => {
console.error(`stderr: ${data}`);
});
ps.on('close', (code) => {
console.log(`child process exited with code ${code}`);
});
Which produces the following example output, running it in docker:
$ docker run --rm -v "$PWD":/usr/src/app -w /usr/src/app node:17-bullseye node ./runps.js
stdout: USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 0.8 319312 33888 ? Ssl 11:08 0:00 node ./runps.js
root 13 0.0 0.0 6700 2844 ? R 11:08 0:00 ps -aux
child process exited with code 0
The thing I like about this module, is that it's included with the Node.js distribution, no npm install ... needed.
If you search the Node.js code in github for spawn you will find references to the implementation in C or C++ in the engine. Modern browsers like Firefox and Chrome would be reluctant to extend JavaScript with such features, for obvious security reasons, even if the underlying engine such as V8 supports it.
On that note, it's better not to run our container as root, let's try the above example again, adding a random user this time.
$ docker run --rm -u 7000 -v "$PWD":/usr/src/app -w /usr/src/app node:17-bullseye node ./runps.js
stdout: USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
7000 1 5.0 0.8 319312 33812 ? Ssl 11:19 0:00 node ./runps.js
7000 13 0.0 0.0 6700 2832 ? R 11:19 0:00 ps -aux
child process exited with code 0
Of course that's better but not enough. If this approach is used at all, more precautions must be taken, such as ensuring that no arbitrary user commands can be executed.
Windows 10
My version of Windows 10 still has Windows Script Host which can run JScript on the console with the wscript.exe or cscript.exe programs, i.e. no browser needed. To try it out you can open a PowerShell Windows Terminal. Save the following code into a file which you can call shell.js:
WScript.StdOut.WriteLine("Hallo, ECMAScript on Windows!");
WScript.CreateObject("WScript.Shell").run("C://Windows//system32//mspaint.exe");
And on the command line, run:
cscript .\shell.js
Which shows the following and opens Paint:
Microsoft (R) Windows Script Host Version 5.812
Copyright (C) Microsoft Corporation. All rights reserved.
Hallo, ECMAScript on Windows!
Other variations exist. Find the documentation applicable to your preferred JavaScript runtime environment.
const fs = require('fs');
function ls(startPath) {
fs.readdir(startPath, (err, entries) => {
console.log(entries);
})
}
ls('/home/<profile_name>/<folder_name>')
The startPath used here is in reference with debian distro
Js file
var oShell = new ActiveXObject("Shell.Application");
oShell.ShellExecute("E:/F/Name.bat","","","Open","");
Bat file
powershell -Command "& {ls | Out-File -FilePath `E:F/Name.txt}"`
Js file run with node namefile.js
const fs = require('fs')
fs.readFile('E:F/Name.txt', (err, data) => {
if (err) throw err;
console.log(data.toString());
})
You can also do everything in one solution with an asynchronous function.
Directly there could be security problems.

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