I'm trying to spawn a process in NodeJS that accesses the my home folder, and can't see, to get either of the options below to work.
var spawn = require('child_process').spawn,
options = {stdio: 'inherit', env: process.env};
spawn('ls', ['~/'], options);
spawn('ls', ['$HOME'], options);
Output
ls: ~/: No such file or directory
ls: $HOME: No such file or directory
I've verified that options.env.HOME is properly set, any idea what I'm doing wrong?
Update
So this is what I ended up doing to make my use-case work (using script instead of ls):
spawn('script', [process.env.HOME], options);
Then, inside of my script:
#!/usr/bin/env bash
export HOME=$1
I still don't understand why options.env.HOME does not seem to work as expected.
process.env.HOME is what you want. Use it like so:
var spawn = require('child_process').spawn,
options = {stdio: 'inherit'};
var ls = spawn('ls', [process.env.HOME]);
ls.stdout.on('data', function(data){
console.log(String(data));
});
ls.stderr.on('data', function(data){
console.log(String(data));
});
Then you can set HOME in your shell when invoking the node script:
HOME='/tmp'; node ls.js
Alternatively, you don't have to overload HOME. To use whatever variable you like export it first, and then access it through process.env.:
export FOO='/tmp'; node ls.js
Related
How to execute the command npm init in the nodejs file? I want to use node. / index.js to execute the command. But what should I do if the command interacts with the user?
This code is directly stuck, and the subsequent question and answer cannot be carried out.I hope users can fill in the information normally
let exec = require('child_process').exec;
exec("npm init")
To allow users to fill in the questionnaire via the CLI, consider using the child_process module's spawn() method instead of exec().
*Nix (Linux, macOS, ... )
For example:
index.js
const spawn = require('child_process').spawn;
spawn('npm', ['init'], {
shell: true,
stdio: 'inherit'
});
Note: After the user has completed the questionnaire this example (above) creates the resultant package.json file in the current working directory, i.e. the same directory from where the node command invoked index.js.
However, If you want to ensure that package.json is always created in the same directory as where index.js resides then set the value of the cwd option to __dirname. For example:
const spawn = require('child_process').spawn;
spawn('npm', ['init'], {
cwd: __dirname, // <---
shell: true,
stdio: 'inherit'
});
Windows
If you are running node.js on Windows then you need to use the following variation instead:
script.js
const spawn = require('child_process').spawn;
spawn('cmd', ['/c', 'npm init'], { //<----
shell: true,
stdio: 'inherit'
});
This also utilizes the spawn() method, however it starts a new instance of Windows command shell (cmd). The /c option runs the npm init command and then terminates.
Cross-platform (Linux, macOS, Windows, ... )
For a cross platform solution, (i.e. one that runs on Windows, Linux, macOS), then consider combining the previous examples to produce the following variation:
script.js
const spawn = require('child_process').spawn;
const isWindows = process.platform === 'win32';
const cmd = isWindows ? 'cmd' : 'npm';
const args = isWindows ? ['/c', 'npm init'] : ['init'];
spawn(cmd, args, {
shell: true,
stdio: 'inherit'
});
Assuming there doesn't need to be any user input you could do:
let exec = require('child_process').exec;
exec("npm init -y")
If I have this script in node, saved as example.js:
const childProcess = require('child_process');
childProcess.spawn('vim', ['-u NONE', 'test.txt'], { stdio: 'inherit' });
I would expect that node example.js would be (roughly) equivalent to calling:
vim -u NONE test.txt
However, when I execute the script I get:
$ node example.js
VIM - Vi IMproved 8.2 (2019 Dec 12, compiled Dec 26 2020 07:37:17)
Garbage after option argument: "-u NONE"
More info with: "vim -h"
Running vim -u NONE example.txt directly works just fine.
Am I misunderstanding / misusing spawn somehow?
Edit:
This, without the -u NONE flag, works just fine:
childProcess.spawn('vim', ['test.txt'], { stdio: 'inherit' });
It's adding -u NONE that for some reason vim doesn't like.
This should work
const cp = spawn('vim', ['test.txt'], {stdio: ['inherit']})
cp.stdout.pipe(process.stdout)
Spawn open a child_process which is attached to the const cp(in this ex), this method stream its output (https://nodejs.org/dist/latest-v14.x/docs/api/child_process.html), so we need to consume it. We pipe the cp.stdout to the parent_process process.stdout. That open a new tty within: the child_process.stdout
We can make it more straightforward by setting the stdio childProcess.output option to 'inherit' and(optional) forwarding the childProcess.stderr to its own childProcess.stdout (which is already inherit by the motherProcess, so will be output automatically).
This should output the same as previously
const cp = spawn(
'vim', ['test.txt'],
{stdio: ['inherit', 'inherit', process.stdout]}
)
To run precisely the command vim -u NONE file.ext. The first argument is the executable path and the second is an array containing the flags to pass to the command. Inside this array each single element(separate with space) of the flags must be an element of the array. So in this case that should work
const cp = spawn(
'vim', ['-u', 'NONE', 'test.txt'],
{stdio: ['inherit', 'inherit', process.stdout]}
)
You could use it like this:
const { exec } = require("child-process");
exec('vim -u NONE example.txt', (err, stdout, stderr) => {
if (err) {
console.error(err);
return;
}
console.log(stdout);
});
In my electron/reactjs app, i'm trying to open a terminal and launch somes commands.
My code looks like this :
const terminal = 'x-terminal-emulator';
const { spawn } = require('child_process');
spawn(terminal);
My terminal opens but i don't know how to launch commands in this terminal like 'cd /my/custom/path && ls'
Can someone help me please ? :)
Node.js child_process.spawn command have an option to specify the shell you want to use.
So I would use the opposite logic and launch directly the command within a particular shell (for exemple bash):
const { spawn } = require('child_process');
const terminal = '/bin/bash';
let cmd = 'echo $SHELL';
spawn(cmd, { shell: terminal })
.stdout.on('data', (data) => {
console.log(`stdout: ${data}`); //-> stdout: /bin/bash
});
I am attempting to run a script that is archived inside an ASAR file like so:
var spawn = require('child_process').spawn;
var t = spawn('node', ['./bundle.asar/main.js'], {});
t.on('data', function(data){
console.log(data.toString());
});
t.stdout.pipe(process.stdout);
t.stderr.pipe(process.stderr);
FYI the above script is situated outside the ASAR archive.
However, all I get is the following error:
Cannot find module 'C:\Users\MyUser\tests\asar-test\bundle.asar\main.js'
The official docs on this particular issue are nonexistent.
Is there some way to either read the ASAR file or require a script inside it?
Thank you.
For posterity, the answer to this is to require your .js file like so:
var spawn = require('child_process').spawn;
var myScript = require('./bundle.asar/main.js');
var t = spawn('node', [myScript], {});
t.on('data', function(data){
console.log(data.toString());
});
t.stdout.pipe(process.stdout);
t.stderr.pipe(process.stderr);
Hope this helps.
I'm on node v4.4.0 and on Windows 10. I'm using bunyan to log my node application.
try {
var fs = require('fs');
var path = require('path');
var spawn = require('child_process').spawn;
var through = require('through');
} catch (err) {
throw err;
}
var prettyStream = function () {
// get the binary directory of bunyan
var bin = path.resolve(path.dirname(require.resolve('bunyan')), '..', 'bin', 'bunyan');
console.log(bin); // this outputs C:\www\nodeapp\src\node_modules\bunyan\bin\bunyan, the file does exist
var stream = through(function write(data) {
this.queue(data);
}, function end() {
this.queue(null);
});
// check if bin var is not empty and that the directory exists
if (bin && fs.existsSync(bin)) {
var formatter = spawn(bin, ['-o', 'short'], {
stdio: [null, process.stdout, process.stderr]
});
// stream.pipe(formatter.stdin); // <- did this to debug
}
stream.pipe(process.stdout); // <- did this to debug
return stream;
}
The logging spits out in the console due to the fact I used stream.pipe(process.stdout);, i did this to debug the rest of the function.
I however receive the error:
Error: spawn C:\www\nodeapp\src\node_modules\bunyan\bin\bunyan ENOENT
at exports._errnoException (util.js:870:11)
at Process.ChildProcess._handle.onexit (internal/child_process.js:178:32)
at onErrorNT (internal/child_process.js:344:16)
at nextTickCallbackWith2Args (node.js:442:9)
at process._tickCallback (node.js:356:17)
at Function.Module.runMain (module.js:443:11)
at startup (node.js:139:18)
at node.js:968:3
I'm guessing this is a Windows error. Anyone have any ideas?
Use {shell: true} in the options of spawn
I was hit with this problem recently so decided to add my findings here. I finally found the simplest solution in the Node.js documentation. It explains that:
child_process.exec() runs with shell
child_process.execFile() runs without shell
child_process.spawn() runs without shell (by default)
This is actually why the exec and spawn behave differently. So to get all the shell commands and any executable files available in spawn, like in your regular shell, it's enough to run:
const { spawn } = require('child_process')
const myChildProc = spawn('my-command', ['my', 'args'], {shell: true})
or to have a universal statement for different operating systems you can use
const myChildProc = spawn('my-command', ['my', 'args'], {shell: process.platform == 'win32'})
Side notes:
It migh make sense to use such a universal statement even if one primairly uses a non-Windows system in order to achieve full interoperability
For full consistence of the Node.js child_process commands it would be helpful to have spawn (with shell) and spawnFile (without shell) to reflect exec and execFile and avoid this kind of confusions.
I got it. On Windows bunyan isn't recognized in the console as a program but as a command. So to invoke it the use of cmd was needed. I also had to install bunyan globally so that the console could access it.
if (!/^win/.test(process.platform)) { // linux
var sp = spawn('bunyan', ['-o', 'short'], {
stdio: [null, process.stdout, process.stderr]
});
} else { // windows
var sp = spawn('cmd', ['/s', '/c', 'bunyan', '-o', 'short'], {
stdio: [null, process.stdout, process.stderr]
});
}
I solved same problem using cross-spawn. It allows me to spawn command on both windows and mac os as one common command.
I think you'll find that it simply can't find 'bunyun', but if you appended '.exe' it would work. Without using the shell, it is looking for an exact filename match to run the file itself.
When you use the shell option, it goes through matching executable extensions and finds a match that way. So, you can save some overhead by just appended the executable extension of your binary.
I was having this same problem when trying to execute a program in the current working directory in Windows. I solved it by passing the options { shell: true, cwd: __dirname } in the spawn() call. Then everything worked, with every argument passed as an array (not attached to the program name being run).
I think, the path of bin or something could be wrong. ENOENT = [E]rror [NO] [ENT]ry