This is the code that i found on the internet:
const { exec } = require('child_process');
var yourscript = exec('sh launch.sh', (error, stdout, stderr) => {
console.log(stdout);
console.log(stderr);
if (error !== null) {
console.log(`exec error: ${error}`);
}
});
and here is my sh file which is in the same file as my previous code:
echo "Hi There!"
but each time I run the program the console shows me:
exec error: Error: Command failed: sh launch.sh
sh: 0: Can't open launch.sh
Can somebody help me with my code please?
First, you seem to have a file permissions issue, so to fix that, start by setting the file permissions for the user as the user needs execution permissions:
chmod 755 launch.sh
Second, the code you found online is using "exec" that is now deprecated in favour of builtin child_process.execFile. So, for your needs the code would look a bit like:
var child_process = require('child_process');
child_process.exec('sh launch.sh', function(error, stdout, stderr){
console.log(stdout);
});
This should help to get started! The inner command sh launch.sh should be executable in the command line, directly, so tested without running the main host or nodejs script! Type the command in your CLI and press enter! Alternatively to calling sh launch.sh do /bin/sh launch.sh
Of course, you might want to look at docs to improve the implementation and fully understand file permissions under your OS, what sh means and finally child_process.exec.
https://www.linux.com/tutorials/understanding-linux-file-permissions
https://en.wikipedia.org/wiki/Bourne_shell
https://nodejs.org/api/child_process.html
I am using the package: https://www.npmjs.com/package/easy-pdf-merge
To merge several PDF files, and it works fine when run from NodeJS.
However when I pack it through Electron-builder I get the following error "Command failed: java -jar" I am guessing it has something to do with Electron-Builder putting node modules into the "app.asar".
I have downloaded Java and added to Path (which means it works fine from CMD)
var merge = require('easy-pdf-merge');
merge(filePaths, 'merged.pdf', function (err) {
if (err) {
console.log('Error: ' + err);
}
resolve('ok');
});
I am not very skilled in either Java or Electron-Builder so any input would be helpful
EDIT:
I have updated code with closing bracket and removed error with opening jar file.
I ended up putting the node module in the app.asar.unpacked folder by modifying package.json with:
"build": {
"asar": true,
"asarUnpack": [
"node_modules/easy-pdf-merge/**/*"
]
},
Afterwards I used the following to reference the node module:
var merge = require(path.join(__dirname, '/../../app.asar.unpacked/node_modules/easy-pdf-merge'));
I'd like to add a self-updating feature to a globally installed module. Is there a better way of doing it than this?
require("child_process").exec("npm update -g module-name");
There's some documentation about installing npm as a local dependency. Is this necessary? Is there any sample code on how to execute commands like update or install ?
Here's what I've usually done to use the system copy of npm instead of installing another copy of npm as a local module:
function loadNpm(cb) {
require('child_process').exec('npm', function(err, stdout, stderr) {
var m = /npm#[^ ]+ (.+)\n/i.exec(stdout);
if (!m)
return cb(new Error('Unable to find path in npm help message'));
cb(undefined, require(m[1]));
});
}
// usage ...
// only need to call `loadNpm()` once
loadNpm(function(err, npm) {
if (err) throw err;
// load() is required before using npm API
npm.load(function(err, npm) {
if (err) throw err;
// e.g. npm.search('ssh', true, function(err, results) { console.dir(results); });
});
});
Depending on your goals, here are a few options:
1) Via exec() as you mention. Don't forget to add an error callback.
2) Using the npm package as you mention.
For example, I wrote a quick script to install the Yeoman package globally which worked well. I didn't see a lot of documentation for this so I started reading the source code in the npm package itself.
var npm = require('npm');
npm.load (function (err, npm) {
if (err) {
console.log("Error loading");
return;
}
npm.config.set('global', true);
npm.commands.install(['yo'], function (err) {
if (err) {
console.error("Installation failed");
}
});
});
3) Another option is to just have a cron job auto-update packages if that is your goal.
4) You may also be interested in this package https://github.com/tjunnone/npm-check-updates
Can you configure other installation commands in yeoman, beyond the standards(bower, npm) that it can run on your self generator?
You are in full control of the generator you write, so there's nothing stopping you from executing any command you would like, including other installation tools.
If you take a look at the install.js file in yeoman-generator you'll see that runInstall (which is run by installDependencies, bowerInstall and npmInstall) just combines some arguments that are then executed by this.spawnCommand:
var args = ['install'].concat(paths).concat(dargs(options));
this.spawnCommand(installer, args, cb)
.on('error', cb)
.on('exit', this.emit.bind(this, installer + 'Install:end', paths))
.on('exit', function (err) {
if (err === 127) {
this.log.error('Could not find ' + installer + '. Please install with ' +
'`npm install -g ' + installer + '`.');
}
cb(err);
}.bind(this));
(Source)
If you want to run a custom tool to install dependencies, you can just define a function like this in your own generator.
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.