I need to print a file using the command line. When doing something like
rundll32 C:\WINDOWS\system32\shimgvw.dll,ImageView_PrintTo "d:\Temp\test.jpg" "Canon_CP1000"
in CMD manually it works just fine and the image gets printed. However, as soon as I use Nodes "spawn" command to achieve the same behaviour it doesn't do anything.
var spawn = require('child_process').spawn;
var cliCmd = spawn('rundll32', [
'C:\\WINDOWS\\system32\\shimgvw.dll,ImageView_PrintTo "d:\\Temp\\test.jpg" "Canon_CP1000"',
]);
cliCmd.stdout.on('data', function (data) {
console.log('stdout', data);
});
cliCmd.stderr.on('data', function (data) {
console.log('stderr', data);
});
There is also no output in the console at all. Other commands in spawn work (e.g. "ipconfig, ['/all']"). I have also tried to separate the space-separated attributes and placing it in an array slot each. No effect.
Help is very much appreciated. Thanks!
Use an array of parameters to pass to span your child process.
var cliCmd = spawn('rundll32.exe', [
'C:\\WINDOWS\\system32\\shimgvw.dll,ImageView_PrintTo', 'd:\\Temp\\test.jpg', 'Canon_CP1000'
]);
Also, make sure you have the full name of rundll32.exe. You might also have to specify its path.
Related
I'm running Windows 10, and I have a program, let's call it program, that can be run from the command line. When run, it responds to commands the user enters. The user enters a command, presses the return key, and the program prints a response. I did not make this program and do not have the source, so I cannot modify it.
I want to run this program from within Node.js, and have my Node.js program act as the user, sending it commands and getting the responses. I spawn my program like this:
var spawn = require('child_process').spawn;
var child = spawn('program');
child.stdout.on('data', function(data) {
console.log(`stdout: ${data}`);
});
Then I attempt to send it a command, for example, help.
child.stdin.write("help\n");
And nothing happens. If I manually run the program, type help, and press the return key, I get output. I want Node.js to run the program, send it input, and receive the output exactly as a human user would. I assumed that stdin.write() would send the program a command as if the user typed it in the console. However, as the program does not respond, I assume this is not the case. How can I send the program input?
I've seen many similar questions, but unfortunately the solutions their authors report as "working" did not work for me.
Sending input data to child process in node.js
I've seen this question and answer and tried everything in it with no success. I've tried ending the command with \r\n instead of \n. I've also tried adding the line child.stdin.end() after writing. Neither of these worked.
How to pass STDIN to node.js child process
This person, in their self-answer, says that they got theirs to work almost exactly as I'm doing it, but mine does not work.
Nodejs Child Process: write to stdin from an already initialised process
This person, in their self-answer, says they got it to work by writing their input to a file and then piping that file to stdin. This sounds overly complicated to send a simple string.
This worked for me, when running from Win10 CMD or Git Bash:
console.log('Running child process...');
const spawn = require('child_process').spawn;
const child = spawn('node');
// Also worked, from Git Bash:
//const child = spawn('cat');
child.stdout.on('data', (data) => {
console.log(`stdout: "${data}"`);
});
child.stdin.write("console.log('Hello!');\n");
child.stdin.end(); // EOF
child.on('close', (code) => {
console.log(`Child process exited with code ${code}.`);
});
Result:
D:\Martin\dev\node>node test11.js
Running child process...
stdout: "Hello!
"
Child process exited with code 0.
I also tried running aws configure like this, first it didn't work because I sent only a single line. But when sending four lines for the expected four input values, it worked.
Maybe your program expects special properties for stdin, like being a real terminal, and therefore doesn't take your input?
Or did you forget to send the EOF using child.stdin.end();? (If you remove that call from my example, the child waits for input forever.)
Here is what worked for me. I have used child_process exec to create a child process. Inside this child process Promise, I am handling the i/o part of the cmd given as parameter. Its' not perfect, but its working.
Sample function call where you dont need any human input.
executeCLI("cat ~/index.html");
Sample function call where you interact with aws cli. Here
executeCLI("aws configure --profile dev")
Code for custom executeCLI function.
var { exec } = require('child_process');
async function executeCLI(cmd) {
console.log("About to execute this: ", cmd);
var child = exec(cmd);
return new Promise((resolve, reject) => {
child.stdout.on('data', (data) => {
console.log(`${data}`);
process.stdin.pipe(child.stdin);
});
child.on('close', function (err, data) {
if (err) {
console.log("Error executing cmd: ", err);
reject(err);
} else {
// console.log("data:", data)
resolve(data);
}
});
});
}
Extract the user input code from browser and save that code into a file on your system using fs module. Let that file be 'program.cpp' and save the user data input in a text file.
As we can compile our c++ code on our terminal using g++ similarly we will be using child_process to access our system terminal and run user's code.
execFile can be used for executing our program
var { execFile } = require('child_process');
execFile("g++", ['program.cpp'], (err, stdout, stderr) => {
if (err) {
console.log("compilation error: ",err);
} else{
execFile ('./a.out' ,['<', 'input.txt'], {shell: true}, (err, stdout, stderr) => {
console.log("output: ", stdout);
})
}
})
In this code we simply require the child_process and uses its execFile function.
First we compile the code present in program.cpp, which creates a default a.out as output file
Then we pass the a.out file with input that is present in input.txt
Hence you can view the generated output in your terminal and pass that back to the user.
for more details you can check: Child Processes
I am having a problem with async shell executes in node.js.
In my case, node.js is installed on a Linux operating system on a raspberry pi. I want to fill an array with values that are parsed from a shell script which is called on the pi. This works fine, however, the exec() function is called asynchronously.
I need the function to be absolute synchron to avoid messing up my whole system. Is there any way to achieve this? Currently I am trying a lib called .exe, but the code still seems to behave asynchron.
Here's my code:
function execute(cmd, cb)
{
child = exec(cmd, function(error, stdout, stderr)
{
cb(stdout, stderr);
});
}
function chooseGroup()
{
var groups = [];
execute("bash /home/pi/scripts/group_show.sh", function(stdout, stderr)
{
groups_str = stdout;
groups = groups_str.split("\n");
});
return groups;
}
//Test
console.log(chooseGroup());
If what you're using is child_process.exec, it is asynchronous already.
Your chooseGroup() function will not work properly because it is asynchronous. The groups variable will always be empty.
Your chooseGroup() function can work if you change it like this:
function chooseGroup() {
execute("bash /home/pi/scripts/group_show.sh", function(stdout, stderr) {
var groups = stdout.split("\n");
// put the code here that uses groups
console.log(groups);
});
}
// you cannot use groups here because the result is obtained asynchronously
// and thus is not yet available here.
If, for some reason, you're looking for a synchronous version of .exec(), there is child_process.execSync() though it is rarely recommended in server-based code because it is blocking and thus blocks execution of other things in node.js while it is running.
First of all, I'm a complete noob and started using Node.JS yesterday (it was also my first time using Linux in years) so please be nice and explicit
I'm currently making a Node.JS program which has to, among other things, launch shell commands (mainly : mount an usb drive).
I'm currently using
var spawn = require('child_process').spawnSync;
function shspawn(command) {
spawn('sh', ['-c', command], { stdio: 'inherit' });
}
shspawn('echo Hello world');
shspawn('mkdir newdir');
etc. which is a really comfortable way to do it for me.
The problem is that I'd like to store the output of, for example, a "ls" command in a variable, in a way like
var result = shspawn('ls -l')
I've read some examples online but they rarely use spawn and when they do, it doesn't work for me (I guess I may do something wrong, but again I'm a noob in Node)
If you guys have a better idea than using child_process_spawnSync I'm open to any idea, but I'd like as long as possible to keep my program package-free :)
EDIT : I need it to work synchronously ! That's why I've started using spawnSync. I will be using some commands like dd, that takes time and needs to be fully finished before the program moves on to another command.
You can do it something like below.
var spawn = require('child_process').spawn;
// Create a child process
var child = spawn('ls' , ['-l']);
child.stdout.on('data',
function (data) {
console.log('ls command output: ' + data);
});
child.stderr.on('data', function (data) {
//throw errors
console.log('stderr: ' + data);
});
child.on('close', function (code) {
console.log('child process exited with code ' + code);
});
Update: with spawnSync
var spawn = require('child_process').spawnSync;
var child = spawn('ls' , ['-l','/usr']);
console.log('stdout here: \n' + child.stdout);
Hi can anyone help me with a custom grunt task?
I'm basically using child_process to call
var cp = exec(cmd, {}, function (err, stdout, stderr) {}
this of course has the stdout etc. If I
cp.stdout.pipe(process.stdout);
it rights a bunch of stuff to the console. I am making this call in a loop so here's a skeleton
this.files.forEach(function(f) {
var src = f.src.map(function(filepath) {
var cmd = util.format("%s %s", options.xUnit, src);
var cp = exec(cmd, {}, function (err, stdout, stderr) {
....
cb();
});
if (options.stdout || grunt.option('verbose')) {
cp.stdout.pipe(process.stdout);
}
This all works fine. but since I'm doing it several times I want at the very least to be able to index how many times stderr has a value. I'm basically running collections of tests. If all pass then stderr is blank if not, I don't want to stop the rest of the tests I want them all to run, but i'd like to output at the end "you have 3 collections that have failing tests". I don't see why I can't seem to get it to work. If I declare
var output = 0;
then
if (options.stderr || grunt.option('verbose')) {
cp.stdout.pipe(process.stdout);
output ++;
}
I then try to print to console after they all run but it's always 0.
I would really like to some how get a copy of ALL the output and parse out the last line from each test session which has the number of tests that failed in it. But that just seems way out of realm of possiblity. I've tried all manner of stuff with the streams and got less than nothing.
Anyway, if anyone can help I would greatly appreciate it
I have a PhantomJS/CasperJS script which I'm running from within a node.js script using process.spawn(). Since CasperJS doesn't support require()ing modules, I'm trying to print commands from CasperJS to stdout and then read them in from my node.js script using spawn.stdout.on('data', function(data) {}); in order to do things like add objects to redis/mongoose (convoluted, yes, but seems more straightforward than setting up a web service for this...) The CasperJS script executes a series of commands and creates, say, 20 screenshots which need to be added to my database.
However, I can't figure out how to break the data variable (a Buffer?) into lines... I've tried converting it to a string and then doing a replace, I've tried doing spawn.stdout.setEncoding('utf8'); but nothing seems to work...
Here is what I have right now
var spawn = require('child_process').spawn;
var bin = "casperjs"
//googlelinks.js is the example given at http://casperjs.org/#quickstart
var args = ['scripts/googlelinks.js'];
var cspr = spawn(bin, args);
//cspr.stdout.setEncoding('utf8');
cspr.stdout.on('data', function (data) {
var buff = new Buffer(data);
console.log("foo: " + buff.toString('utf8'));
});
cspr.stderr.on('data', function (data) {
data += '';
console.log(data.replace("\n", "\nstderr: "));
});
cspr.on('exit', function (code) {
console.log('child process exited with code ' + code);
process.exit(code);
});
https://gist.github.com/2131204
Try this:
cspr.stdout.setEncoding('utf8');
cspr.stdout.on('data', function(data) {
var str = data.toString(), lines = str.split(/(\r?\n)/g);
for (var i=0; i<lines.length; i++) {
// Process the line, noting it might be incomplete.
}
});
Note that the "data" event might not necessarily break evenly between lines of output, so a single line might span multiple data events.
I've actually written a Node library for exactly this purpose, it's called stream-splitter and you can find it on Github: samcday/stream-splitter.
The library provides a special Stream you can pipe your casper stdout into, along with a delimiter (in your case, \n), and it will emit neat token events, one for each line it has split out from the input Stream. The internal implementation for this is very simple, and delegates most of the magic to substack/node-buffers which means there's no unnecessary Buffer allocations/copies.
I found a nicer way to do this with just pure node, which seems to work well:
const childProcess = require('child_process');
const readline = require('readline');
const cspr = childProcess.spawn(bin, args);
const rl = readline.createInterface({ input: cspr.stdout });
rl.on('line', line => /* handle line here */)
Adding to maerics' answer, which does not deal properly with cases where only part of a line is fed in a data dump (theirs will give you the first part and the second part of the line individually, as two separate lines.)
var _breakOffFirstLine = /\r?\n/
function filterStdoutDataDumpsToTextLines(callback){ //returns a function that takes chunks of stdin data, aggregates it, and passes lines one by one through to callback, all as soon as it gets them.
var acc = ''
return function(data){
var splitted = data.toString().split(_breakOffFirstLine)
var inTactLines = splitted.slice(0, splitted.length-1)
var inTactLines[0] = acc+inTactLines[0] //if there was a partial, unended line in the previous dump, it is completed by the first section.
acc = splitted[splitted.length-1] //if there is a partial, unended line in this dump, store it to be completed by the next (we assume there will be a terminating newline at some point. This is, generally, a safe assumption.)
for(var i=0; i<inTactLines.length; ++i){
callback(inTactLines[i])
}
}
}
usage:
process.stdout.on('data', filterStdoutDataDumpsToTextLines(function(line){
//each time this inner function is called, you will be getting a single, complete line of the stdout ^^
}) )
You can give this a try. It will ignore any empty lines or empty new line breaks.
cspr.stdout.on('data', (data) => {
data = data.toString().split(/(\r?\n)/g);
data.forEach((item, index) => {
if (data[index] !== '\n' && data[index] !== '') {
console.log(data[index]);
}
});
});
Old stuff but still useful...
I have made a custom stream Transform subclass for this purpose.
See https://stackoverflow.com/a/59400367/4861714
#nyctef's answer uses an official nodejs package.
Here is a link to the documentation: https://nodejs.org/api/readline.html
The node:readline module provides an interface for reading data from a Readable stream (such as process.stdin) one line at a time.
My personal use-case is parsing json output from the "docker watch" command created in a spawned child_process.
const dockerWatchProcess = spawn(...)
...
const rl = readline.createInterface({
input: dockerWatchProcess.stdout,
output: null,
});
rl.on('line', (log: string) => {
console.log('dockerWatchProcess event::', log);
// code to process a change to a docker event
...
});