I have a simple nodejs server up and running. I am running into trouble when I try to spawn a child process. the jar file I am trying to access, is in the same directory as the node script. It takes in a command line argument that I am trying to pass in and it outputs data to the command line, which I am trying to pipe into the var child.
var child = require('child_process').spawn('java -jar done.jar',['argument to pass in']);
child.stdout.on('data', function(data) {
console.log(data.toString());
});
child.stderr.on("data", function (data) {
console.log(data.toString());
});
This produces the following error message:
events.js:85
throw er; // Unhandled 'error' event
^
Error: spawn java -jar done.jar ENOENT
at exports._errnoException (util.js:746:11)
at Process.ChildProcess._handle.onexit (child_process.js:1046:32)
at child_process.js:1137:20
at process._tickCallback (node.js:355:11)
Any ideas?
You're executing java. -jar and done.jar are arguments to pass.
var child = require('child_process').spawn(
'java', ['-jar', 'done.jar', 'argument to pass in']
);
You will also need to specify the full path to java, or make sure that java is specified in the OS path.
Related
const { spawn } = require("child_process")
try{
spawn("invalid/path/to/executable")
}catch(err){
console.log("exception: ",err)
}
This code raises an error and the execution of the program stops. It never prints exception: so the catch block is not executed:
events.js:183
throw er; // Unhandled 'error' event
^
Error: spawn invalid/path/to/executable ENOENT
When run with a valid path to an executable, the same code works.
What can I do to handle the case when the spawn fails due to ENOENT error?
This module fires error event and you can just add a listener for it.
You can read more about it here
So, you can transform your code to:
const {spawn} = require("child_process")
const subprocess = spawn("invalid/path/to/executable")
subprocess.on('error', function (err) {
console.log('Failed to start subprocess: ' + err);
});
Also, I suggest reading this article by Samer Buna. He covered a lot of interesting topics about this module.
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
Whenever the appropriate files change I would like to bundle my tests and start karma, showing any failed tests.
I currently have the watch task:
gulp.task('default', ['browserify', 'css','runTests'], function () {
gulp.watch('./src/js/**/*.js', ['browserify']);
gulp.watch('./src/js/**/*.js', ['runTests']);
});
Which starts up the runTests.js
var testFile = [
'./src/components/tests/suite.js'
];
// bundle tests
var cmd = child.spawn('browserify', ['-e', './src/components/tests/suite.js', '-t', 'reactify', '-t']);
cmd.on('close', function (code) {
//cmd finished start karma
gulp.src(testFiles)
.pipe(karma({
configFile: 'karma.conf.js',
action: 'run'
}))
.on('error', function(err) {
throw err;
});
});
my console currently errors here:
[17:04:27] Starting 'runTests'...
[17:04:27] Finished 'runTests' after 2.73 ms
events.js:85
throw er; // Unhandled 'error' event
^
Error: spawn browserify ENOENT
at exports._errnoException (util.js:746:11)
at Process.ChildProcess._handle.onexit (child_process.js:1053:32)
at child_process.js:1144:20
at process._tickCallback (node.js:355:11)
at Function.Module.runMain (module.js:503:11)
at startup (node.js:129:16)
at node.js:814:3
Process finished with exit code 1
I can get a basic command to work child = spawn("ls");
But not the browserify command, can anyone help?
You can use the browserify API within a gulp task. Look at substack/node-browserify#1170 for some tips on globbing with browserify. Then you can just include the output file in your karam config files array.
// Disclaimer: This code is untested
var files = require("glob").sync('./src/js/**/*.js');
files.push('./src/components/tests/suite.js');
var browserify = require("browserify")(files, {transform: 'reactify'});
// your can do more config on the browserify instance
// Run browserify bundle and output to a file
var myFile = require('fs').createWriteStream('myOutput.txt');
browserify.bundle().pipe(myFile);
I use Node.js.
My server js script I run such:
node chat_server.js
After I get errors messages in terminal CentOS:
Express server listening on port undefined in development mode.
+ User undefined connected node_redis: no callback to send error: ERR wrong number of arguments for 'sadd' command
/home/who/public_html/node/node_modules/redis/index.js:582
throw err;
^ Error: ERR wrong number of arguments for 'sadd' command
at ReplyParser. (/home/who/public_html/node/node_modules/redis/index.js:317:31)
at ReplyParser.emit (events.js:95:17)
at ReplyParser.send_error (/home/who/public_html/node/node_modules/redis/lib/parser/javascript.js:296:10)
at ReplyParser.execute (/home/who/public_html/node/node_modules/redis/lib/parser/javascript.js:181:22)
at RedisClient.on_data (/home/who/public_html/node/node_modules/redis/index.js:547:27)
at Socket. (/home/who/public_html/node/node_modules/redis/index.js:102:14)
at Socket.emit (events.js:95:17)
at Socket. (_stream_readable.js:748:14)
at Socket.emit (events.js:92:17)
at emitReadable_ (_stream_readable.js:410:10)
Excuse me, but I do not understand the reason of these errors.
On what I should get attention and how fix it?
For example, I use command redis SADD: redis_cli.sadd( "user.friend:" + currentIdUser, data.idUser);
I have done a experiment, created a new text script:
var redis = require("redis");
var client = redis.createClient();
client.on("error", function (err) {
console.log("Error " + err);
});
client.sadd("users","naveen",function(err,reply){
console.log('Ok');
if(err)
throw err;
return reply;
});
It have given me in console: OK. It mean, that all works fine.
I think in my code:
redis_cli.sadd("userslist", currentIdUser);
the variable currentUser is simply empty or undefined. It gives me the next errors.
Problem was at my script in line:
redis_cli.sadd("userslist", currentIdUser);
The variable is undefined. It calls error redis.
Thank you all for help.
I've made an node.js app to list all .txt files from a directory recursively and, for each one, do some stuff.
Here's my app.js:
var spawn = require('child_process').spawn,
dir = spawn('dir', ['*.txt', '/b']);
dir.stdout.on('data', function (data) {
//do some stuff with each stdout line...
console.log('stdout: ' + data);
});
dir.stderr.on('data', function (data) {
//throw errors
console.log('stderr: ' + data);
});
dir.on('close', function (code) {
console.log('child process exited with code ' + code);
});
When I run node app.js via console, I get the error message below:
events.js:72
throw er; // Unhandled 'error' event
^
Error: spawn ENOENT
at errnoException (child_process.js:980:11)
at Process.ChildProcess._handle.onexit (child_process.js:771:34)
I'm using node v0.10.13 at win32 environment.
I do this way (spawn) because I want to handle stdout line by line (the exec method release entire stdout as one string).
* UPDATE *
By the way, using spawn for child_process does not guarantee that the output for cmd dir will be line by line. I've created a question for that too.
That happen because dir is not a executable in Windows. It's a command from the shell.
The solution for your problem is the following:
var dir = spawn('cmd', ['/c', 'dir']);
dir.stdout.on("data", function() {
// do things
})
This exact problem was here also.
Several things:
dir is not a real executable in windows, so node.js cannot find the program you want to run.
You didn't bind an 'error' handler to your child process and the event was turned into an exception that crashed your node instance. Do this:
dir.on('error', function (err) {
console.log('dir error', err);
});
Use fs.readdir instead. It's a standard node.js API that does the same thing.