I need to execute one of the npm scripts from a different node project.
What I tried:
const installingf = spawn('cd', ['[path to directory]', '&&', 'npm', 'run', 'test']);
installingf.on('message', (data) => {
console.log(`stdout: ${data}`);
});
installingf.on('error', (data) => {
console.log(`stderr: ${data}`);
});
installingf.on('close', (code) => {
console.log(`child process exited with code ${code}`);
});
but it does not work. It shows child process exited with code 0 .
I tried mkdir to test if it gets executed but there are no directories created, it exits with code 0 but script is not executed.
Please help me figure out how to do this and if I am doing something wrong.
Maybe is because you're trying to execute one command, but you don't run the cmd.
The cd command doesn't exist on windows as long as you didn't create an alias. So you would need to run 'cmd' with arguments to run.
const spawn = require('child_process').spawn;
const bat = spawn('cmd.exe', ['/c','calc.exe']);
bat.stdout.on('data', (data) => {
console.log(data);
});
bat.stderr.on('data', (data) => {
console.log(data);
});
bat.on('closed', (code) => {
alert(`Child exited with code ${code}`);
});
IMPORTANT to read.
Related
I wrote java program that takes one argument and writes it.
Also, it reads lines and writes them.
Then, I compiled it and ran from Typescript (vscode extension).
const { spawn } = require('node:child_process');
const runJava = spawn('java', ['-cp', 'extension1/src', 'package.Main', 'aaa']);
runJava.stdout.on('data', (data: String) => {
console.log(`stdout: ${data}`);
});
runJava.stderr.on('data', (data: String) => {
console.error(`stderr: ${data}`);
});
runJava.on('close', (code: Number) => {
console.log(`child process exited with code ${code}`);
});
It writes 'aaa' to stdout successfully.
What do I need to do next to send some text to it?
I tried to write with echo, but that didn't work.
Consider a simple example below where I'm printing the response from a long-running command as it sends.
const { spawn } = require('child_process');
const ping = spawn('ping', ['www.google.com']);
ping.stdout.on('data', (data) => {
console.log(`stdout: ${data}`);
});
ping.stderr.on('data', (data) => {
console.error(`stderr: ${data}`);
});
ping.on('close', (code) => {
if (code !== 0) {
console.log(`ping process exited with code ${code}`);
}
});
This works ok. But when I try to pipe this result to grep, it stops working.
See sample below
const { spawn } = require('child_process');
const ping = spawn('ping', ['www.google.com']);
const grep = spawn('grep', ['bytes'])
ping.stdout.on('data', (data) => {
grep.stdin.write(data)
});
ping.stderr.on('data', (data) => {
console.error(`stderr: ${data}`);
});
ping.on('close', (code) => {
if (code !== 0) {
console.log(`ping process exited with code ${code}`);
}
grep.stdin.end();
});
grep.stdout.on('data', (data) => {
console.log(`stdout: ${data}`);
});
grep.stderr.on('data', (data) => {
console.error(`stderr: ${data}`);
});
grep.on('close', (code) => {
console.log(`grep process exited with code ${code}`);
});
The above code does not give me any results.
It looks like it is waiting for the first command to end before it pipes the result to the next.
I observed this by experimenting with the ls command.
Isn't the whole point of piping not to wait? Or am I missing something here?
Some variations I tried to no success:
ping.stdout.pipe(grep.stdin); instead of grep.stdin.write(data), although I don't believe there is much difference between the two.
const ping = spawn('sh', ['-c', 'ping www.google.com | grep bytes']); I have tried this with non-long-running commands and it works ok including the pipe and everything.
The problem is that grep block-buffers its output by default, so until several kilobytes of output are available, it won't send anything back to node. Note that if you waited long enough with your program as-is, you'd eventually see dozens of lines all suddenly returned at once. The --line-buffered option changes this, so do spawn('grep', ['--line-buffered', 'bytes']) instead of spawn('grep', ['bytes']).
I am creating an electron desktop app, and I have code use spawn() with option detached: true. My purpose is to let the child process keep running even when the parent process terminated.
const spawn = require('child_process').spawn;
const ls = spawn('ls', ['-lh', '/usr'], { detached: true });
ls.stdout.on('data', (data) => {
console.log(`stdout: ${data}`);
fs.writeFileSync('path-to-test.txt', 'stdout');
});
ls.stderr.on('data', (data) => {
console.log(`stderr: ${data}`);
fs.writeFileSync('path-to-test.txt', 'stderr');
});
ls.on('close', (code) => {
console.log(`child process exited with code ${code}`);
});
squirrel events https://github.com/electron/grunt-electron-installer#handling-squirrel-events:
switch (squirrelCommand) {
case '--squirrel-install':
case '--squirrel-updated':
app.quit();
return true;
case '--squirrel-uninstall':
app.quit();
return true;
case '--squirrel-obsolete':
return true;
}
I tested the above code outside of squirrel events, it works well when the parent process is alive. But after I put these code inside squirrel events like --squirrel-uninstall (the parent process may terminated before/during child process run), it can only run commands, any code inside it (like fs function) doesn't work any more.
My have a question is: despite of squirrel event, can the logic code like fs inside child process work after the node parent process terminate?
I need to put all the commands in a batch file (test.cmd) with some logic, for example:
IF condition1 (c:\Windows\System32\schtasks.exe /Create ...)
Else (c:\Windows\System32\schtasks.exe /delete ...)
If remove the if-else statement, and only leave one command in test.cmd, by using code like this can execute the command:
exec('some-path/test.cmd', (error, stdout, stderr) => {
if (error) {
console.log(error);
return;
}
console.log(stdout);
});
If add if-else statement back, does anyone know how can I pass parameter from node.js exec() function? In the terminal, it is easy to pass parameters like "test.cmd para1".
Yo can use node spawn.
Example variables
const spawn = require('child_process').spawn;
const ls = spawn('ls', ['-lh', '/usr']);
ls.stdout.on('data', (data) => {
console.log(`stdout: ${data}`);
});
ls.stderr.on('data', (data) => {
console.log(`stderr: ${data}`);
});
ls.on('close', (code) => {
console.log(`child process exited with code ${code}`);
});
documentation:
https://nodejs.org/api/child_process.html
I am wondering what the correct way is to add "execArgs" to a Node process -
we have:
const cp = require('child_process');
const n = cp.spawn('node', ['some-file.js'], {});
but what if I want to add an execArg like so:
const n = cp.spawn('node --harmony', ['some-file.js'], {});
I don't think that is the right way to do it, and the docs don't seem to demonstrate this?
Is this the correct way?
const n = cp.spawn('node', ['--harmony','some-file.js'], {});
According to the docs for child_process.spawn() it clearly states that args is an array of string arguments that is passed in as the second argument.
The child_process.spawn() method spawns a new process using the given command, with command line arguments in args. If omitted, args defaults to an empty array.
A third argument may be used to specify additional options, with these defaults:
{ cwd: undefined, env: process.env }
Example of running ls -lh /usr, capturing stdout, stderr, and the exit code:
const spawn = require('child_process').spawn;
const ls = spawn('ls', ['-lh', '/usr']);
ls.stdout.on('data', (data) => {
console.log(`stdout: ${data}`);
});
ls.stderr.on('data', (data) => {
console.log(`stderr: ${data}`);
});
ls.on('close', (code) => {
console.log(`child process exited with code ${code}`);
});
Based on the above pulled from the child_process docs, the below would be correct.
const n = cp.spawn('node', ['--harmony','some-file.js']);