How can I run a command line and get the outputs as soon as available to show them somewhere.
For example if a run ping command on a linux system, it will never stop, now is it possible to get the responses while the command is still processing ?
Or let's take apt-get install command, what if i want to show the progress of the installation as it is running ?
Actually i'm using this function to execute command line and get outputs, but the function will not return until the command line ends, so if i run a ping command it will never return!
var sys = require('sys'),
exec = require('child_process').exec;
function getOutput(command,callback){
exec(
command,
(
function(){
return function(err,data,stderr){
callback(data);
}
}
)(callback)
);
}
Try using spawn instead of exec, then you can tap into the stream and listen to the data and end events.
var process = require('child_process');
var cmd = process.spawn(command);
cmd.stdout.on('data', function(output){
console.log(output.toString()):
});
cmd.on('close', function(){
console.log('Finished');
});
//Error handling
cmd.stderr.on('data', function(err){
console.log(err);
});
See the Node.js documentation for spawn here: https://nodejs.org/api/child_process.html#child_process_child_process_spawn_command_args_options
Related
I am trying to execute a nodejs file called create-MySwitch.js through a child process in my main.js file.
this is the code for main.js
const exec = require('child_process').exec;
var cmdStr = 'node /home/pi/Desktop/lan-device/create-MySwitch.js';
exec(cmdStr,
{argv: {
port:8080,
uuid:'MyThing'
}},
(error, stdout, stderr)=>{
if (error) {
console.error('exec error: ${error}');
console.log(error);
return;
}
console.log('stdout: ${stdout}');
console.log('stderr: ${stderr}');
});
This is how I am attempting to access the arguments in the create-MySwitch.js file
var port_value = process.argv.port;
var uuid_value = process.argv.uuid;
The output is
stdout: ${stdout}
stderr: ${stderr}
when I run the command
node main.js
I do not think it's working because the output from executing the create-MySwitch.js file should be 'ready', but clearly is not being printed in the stdout variable from the child process.
Essentially, what I am trying to do is run the command 'node createMySwitch.js ', but instead of just typing this in to the command prompt I want to run that command using a child process.
I am doing all of this using the raspbian operating system.
I'm trying to do a little application with node.js that would run on mac and execute some commands.
I've successfully used spawn to run command lines such as xcodebuild, but xcrun doesn't seems to work when I try to open the iOS Simulator.
I can open on terminal by typing:
xcrun instruments -w 'iPhone 5s (9.2)' -t <template>
But if I use node and try to use spawn like this:
var args = ['instruments', '-w', `iPhone 5s (9.2)`, '-t', 'noTemp'];
var xcrun = spawn('xcrun', args);
So it got me thinking that maybe it had some limitation opening apps? I tried to run:
var args = ['/Applications/Spotify.app'];
var xcrun = spawn('open', args);
And nothing happens. I couldn't find anything related to that. My question is: is there anyway to open apps using node.js spawn? If there is, does someone know what's the problem with my code?
Here's the full code if needed:
var args = ['instruments', '-w', `${fullDevice}`, '-t', 'noTemp'];
var xcrun = spawn('xcrun', args);
xcrun.stdout.on('data', (data)=>{
console.log(data.toString('utf8'));
})
xcrun.on('close', (code) => {
socket.emit({
time: commands.getCurrentTime(),
type: 'success',
log: 'Device booted...'
});
callback();
if (code !== 0) {
console.log(`open process exited with code ${code}`);
}
});
OBS: if I run this piece of code the application doesn't terminate, the program doesn't continue and nothing happens.
EDIT: Changed:
xcrun.on('data', (data)=>{
To:
xcrun.stdout.on('data', (data)=>{
Spawned processes have two separate streams for stdout and stderr, so you will need to listen for data on those objects and not the spawned process object itself:
xcrun.stdout.on('data', function(data) {
console.log('stdout: ' + data.toString());
});
xcrun.stderr.on('data', function(data) {
console.log('stderr: ' + data.toString());
});
The problem was one line above. Not sure why, but there's a socket.emit call that is wrong and actually hold the program's execution.
When i run this pidof command by hand, it works. Then put into my server.js.
// send signal to start the install script
var spw = cp.spawn('/sbin/pidof', ['-x', 'wait4signal.py', '|', 'xargs', 'kill', '-USR1']);
spw.stderr.on('data', function(data) {
res.write('----- Install Error !!! -----\n');
res.write(data.toString());
console.log(data.toString());
});
spw.stdout.on('data', function(data) {
res.write('----- Install Data -----\n');
res.write(data.toString());
console.log(data.toString());
});
spw.on('close', function(data) {
res.end('----- Install Finished, please to to status page !!! -----\n');
console.log('88');
});
In the web i only see "----- Install Finished, please to to status page !!!". My install script seems never get this USR1 signal. Anything wrong please ?
The problem is that you have two separate commands. You are piping the output of your /sbin/pidof command to the input stream of your xargs command. If you are using spawn (rather than exec, which a string exactly as you would write on the command line), you need to spawn one process per command.
Spawn your processes like this:
const pidof = spawn('/sbin/pidof', ['-x', 'wait4signal.py']);
const xargs = spawn('xargs', ['kill', '-USR1']);
Now pipe the output of the first process to the input of the second, like so:
pidof.stdout.pipe(xargs.stdin);
Now you can listen to events on your xargs process, like so:
xargs.stdout.on('data', data => {
console.log(data.toString());
});
I'd like to use the execSync method which was added in NodeJS 0.12 but still have the output in the console window from which i ran the Node script.
E.g. if I run a NodeJS script which has the following line I'd like to see the full output of the rsync command "live" inside the console:
require('child_process').execSync('rsync -avAXz --info=progress2 "/src" "/dest"');
I understand that execSync returns the ouput of the command and that I could print that to the console after execution but this way I don't have "live" output...
You can pass the parent´s stdio to the child process if that´s what you want:
require('child_process').execSync(
'rsync -avAXz --info=progress2 "/src" "/dest"',
{stdio: 'inherit'}
);
You can simply use .toString().
var result = require('child_process').execSync('rsync -avAXz --info=progress2 "/src" "/dest"').toString();
console.log(result);
Edit: Looking back on this, I've realised that it doesn't actually answer the specific question because it doesn't show the output to you 'live' — only once the command has finished running.
However, I'm leaving this answer here because I know quite a few people come across this question just looking for how to print the result of the command after execution.
Unless you redirect stdout and stderr as the accepted answer suggests, this is not possible with execSync or spawnSync. Without redirecting stdout and stderr those commands only return stdout and stderr when the command is completed.
To do this without redirecting stdout and stderr, you are going to need to use spawn to do this but it's pretty straight forward:
var spawn = require('child_process').spawn;
//kick off process of listing files
var child = spawn('ls', ['-l', '/']);
//spit stdout to screen
child.stdout.on('data', function (data) { process.stdout.write(data.toString()); });
//spit stderr to screen
child.stderr.on('data', function (data) { process.stdout.write(data.toString()); });
child.on('close', function (code) {
console.log("Finished with code " + code);
});
I used an ls command that recursively lists files so that you can test it quickly. Spawn takes as first argument the executable name you are trying to run and as it's second argument it takes an array of strings representing each parameter you want to pass to that executable.
However, if you are set on using execSync and can't redirect stdout or stderr for some reason, you can open up another terminal like xterm and pass it a command like so:
var execSync = require('child_process').execSync;
execSync("xterm -title RecursiveFileListing -e ls -latkR /");
This will allow you to see what your command is doing in the new terminal but still have the synchronous call.
Simply:
try {
const cmd = 'git rev-parse --is-inside-work-tree';
execSync(cmd).toString();
} catch (error) {
console.log(`Status Code: ${error.status} with '${error.message}'`;
}
Ref: https://stackoverflow.com/a/43077917/104085
// nodejs
var execSync = require('child_process').execSync;
// typescript
const { execSync } = require("child_process");
try {
const cmd = 'git rev-parse --is-inside-work-tree';
execSync(cmd).toString();
} catch (error) {
error.status; // 0 : successful exit, but here in exception it has to be greater than 0
error.message; // Holds the message you typically want.
error.stderr; // Holds the stderr output. Use `.toString()`.
error.stdout; // Holds the stdout output. Use `.toString()`.
}
When command runs successful:
Add {"encoding": "utf8"} in options.
execSync(`pwd`, {
encoding: "utf8"
})
How would I respond to a command line prompt programmatically with node.js? For example, if I do process.stdin.write('sudo ls'); The command line will prompt for a password. Is there an event for 'prompt?'
Also, how do I know when something like process.stdin.write('npm install') is complete?
I'd like to use this to make file edits (needed to stage my app), deploy to my server, and reverse those file edits (needed for eventually deploying to production).
Any help would rock!
You'll want to use child_process.exec() to do this rather than writing the command to stdin.
var sys = require('sys'),
exec = require('child_process').exec;
// execute the 'sudo ls' command with a callback function
exec('sudo ls', function(error, stdout, stderr){
if (!error) {
// print the output
sys.puts(stdout);
} else {
// handle error
}
});
For the npm install one you might be better off with child_process.spawn() which will let you attach an event listener to run when the process exits. You could do the following:
var spawn = require('child_process').spawn;
// run 'npm' command with argument 'install'
// storing the process in variable npmInstall
var npmInstall = spawn('npm', ['install'], {
cwd: process.cwd(),
stdio: 'inherit'
});
// listen for the 'exit' event
// which fires when the process exits
npmInstall.on('exit', function(code, signal) {
if (code === 0) {
// process completed successfully
} else {
// handle error
}
});