Hey everyone, I’m trying to use Blynk to start/stop some programs on Raspberry Pi. The start/stop commands are basic Bash commands. I’ve looked around, but I don’t see people using Blynk to execute Bash commands. What is the best way to do this?
Thanks!
While I do have Blynk running on NodeJS, I am not very proficient in either JS or Linux, however since Blynk works with Javascript, I guess that however a bash command works with JS will work in a Blynk NodeJS script.
Google came up with a few sites that seem to give some good examples… heck, I almost understood some of them 
I just might have to dust off my brain and try some more RPi work.
thanks @Gunner that looks like a good place to start. I am so very unfamiliar with Javascript that I just don’t even know where to begin, so that was helpful.
What I’m trying to do is
[press button in blynk] -> [run one set of scripts to turn off two programs and turn on one other program]
for 3 different programs on the pi
Seems pretty easy and I have a good idea how to do it in python… but JS … ¯_(ツ)_/¯
Well, after reading a few of those topics found with Google, I was able to merge in a small “run the command ifconfig” snippet into my RPi test sketch when pressing a button on V5… after some syntax fiddling, it seems to work.
This NodeJS example might help you get started. (NOTE: mine is setup for my Local Server, so you will need to adjust accordingly.)
var Gpio = require('onoff').Gpio; // links variable 'Gpio' to the all important onoff GPIO control library
var Blynk = require('blynk-library'); // Links variable 'Blynk' to the Blynk Library
var AUTH = 'cda957435xxxxxxx283c95018f'; // My top secret auth code... useless to anyone on the cloud ;P
var blynk = new Blynk.Blynk(AUTH, options = { connector : new Blynk.TcpClient( options = { addr:"10.10.3.13", port:8442 } ) });
var process = require('child_process'); // Allows this script to run CLI commands? Used in the "run the command ifconfig" function
var v1 = new blynk.VirtualPin(1); // Setup Button Widget on V1 with variable 'v1'
var v5 = new blynk.VirtualPin(5); // Setup Button Widget on V5 with variable 'v5'
var v9 = new blynk.VirtualPin(9); // Setup Display Widget on V9 with variable 'v9'
var v10 = new blynk.VirtualPin(10); // Setup LED Widget on V10 with variable 'v10'
v1.on('write', function(param) { // Watches for V1 Button
console.log('V1:', param[0]); // prints value to CLI
if (param == 0) {
blynk.virtualWrite(10, 0); // V10 Widget (ORANGE) LED OFF
} else if (param == 1) {
blynk.virtualWrite(10, 1023); // V10 Widget (ORANGE) LED ON
}
});
// "run the command ifconfig"
v5.on('write', function(param) { // Watches for V5 Button
console.log('V5:', param[0]); // prints value to CLI
if (param == 1) { // Runs the CLI command ifconfig if the button on V5 is pressed
process.exec('ifconfig',function (err,stdout,stderr) {
if (err) {
console.log("\n"+stderr);
} else {
console.log(stdout);
}
})
}
});
v9.on('read', function() { // I don't understand why this says read??
v9.write(new Date().getSeconds()); // but this sends the seconds 0-59 to the Display Widget
});
led = new Gpio(18, 'out'), // Sets up the BCM pin 18 as an output for the LED and assigns it to variable "led"
button = new Gpio(25, 'in', 'both'); // Sets up the BCM pin 25 as an input registering both rising and falling for the variable "button"
button.watch(function (err, value) { // Watches for button press and assigns 0/1 to value
if (err) {
throw err; // Some form of error handling
}
led.writeSync(value); // Sends value (0/1) to Physical LED
if (value == 0) {
blynk.virtualWrite(2, 0); // V2 Widget (BLUE) LED off
blynk.virtualWrite(3, 1023); // V3 Widget (RED) LED on
} else if (value == 1) {
blynk.virtualWrite(2, 1023); // V2 (BLUE) Widget LED on
blynk.virtualWrite(3, 0); // V3 (RED) Widget LED off
}
});
Thanks for that!
Here’s what I’ve got so far, a little program that selects from 3 different audio inputs on the Pi
var Blynk = require('blynk-library');
var AUTH = 'nothistime';
var blynk = new Blynk.Blynk(AUTH, options = {
connector : new Blynk.TcpClient()
});
var exec = require('child_process').exec, child;
var v0 = new blynk.VirtualPin(0);
var v1 = new blynk.VirtualPin(1);
var v2 = new blynk.VirtualPin(2);
var v3 = new blynk.VirtualPin(3);
var slider = new blynk.VirtualPin(4);
var writeVal = '';
//volume control using slider
slider.on('write', function(param) {
child = exec('amixer set PCM ' + param[0] + '%',
function (error, stdout, stderr) {
console.log('stdout: ' + stdout);
console.log('stderr: ' + stderr);
if (error !== null) {
console.log('exec error: ' + error);
}
});
});
//turn on squeezelite turn off others
v1.on('write', function(param) {
child = exec('sudo killall -15 ecasound ;\
sudo systemctl stop shairport-sync ;\
sudo /etc/init.d/squeezelite start',
function (error, stdout, stderr) {
console.log('stdout: ' + stdout);
console.log('stderr: ' + stderr);
if (error !== null) {
console.log('exec error: ' + error);
}
});
writeVal = 'squeezelite ON';
});
//turn on shairport and turn off others
v2.on('write', function(param) {
child = exec('sudo killall -15 ecasound ;\
sudo /etc/init.d/squeezelite stop ;\
sudo systemctl start shairport-sync',
function (error, stdout, stderr) {
console.log('stdout: ' + stdout);
console.log('stderr: ' + stderr);
if (error !== null) {
console.log('exec error: ' + error);
}
});
writeVal = 'shairport ON';
});
//turn on ecasound (analog input) and turn off others
v3.on('write', function(param) {
child = exec('sudo systemctl stop shairport-sync ;\
sudo /etc/init.d/squeezelite stop ;\
ecasound -C -q -B:rt -b:1024 -f:16,2,48000 -i:alsahw,1,0',
function (error, stdout, stderr) {
console.log('stdout: ' + stdout);
console.log('stderr: ' + stderr);
if (error !== null) {
console.log('exec error: ' + error);
}
});
writeVal = 'analog input ON';
});
v0.on('read', function() {
v0.write(writeVal);
});
It seems to work okay, it does crash sometimes when I switch from input to input, so I’ll probably rewrite it as one button turns one input on/off, so I can have all 3 running if I want and I’m not trying to close programs that aren’t running.
Thanks again 
just to share my success, I was able to get the buttons to read as switches to enable on/off of the individual programs. Seems to work pretty well - more stable than the previous version.
I hope it will help someone else 
I used this video as my guide: https://youtu.be/LJ3ic8C8CcA
var Blynk = require('blynk-library');
var AUTH = 'almostmissedit';
var blynk = new Blynk.Blynk(AUTH, options = {
connector : new Blynk.TcpClient()
});
var exec = require('child_process').exec, child;
var v0 = new blynk.VirtualPin(0);
var v1 = new blynk.VirtualPin(1);
var v2 = new blynk.VirtualPin(2);
var v3 = new blynk.VirtualPin(3);
var slider = new blynk.VirtualPin(4);
var writeVal = '';
//volume control using slider
slider.on('write', function(param) {
child = exec('amixer set PCM ' + param[0] + '%',
function (error, stdout, stderr) {
console.log('stdout: ' + stdout);
console.log('stderr: ' + stderr);
if (error !== null) {
console.log('exec error: ' + error);
}
});
});
//turn on squeezelite turn off others
v1.on('write', function(param) {
if (param[0] == '1') {
child = exec('sudo /etc/init.d/squeezelite start',
function (error, stdout, stderr) {
console.log('stdout: ' + stdout);
console.log('stderr: ' + stderr);
if (error !== null) {
console.log('exec error: ' + error);
}
});
writeVal = 'squeezelite ON';
}
else if (param[0] == '0') {
child = exec('sudo /etc/init.d/squeezelite stop',
function (error, stdout, stderr) {
console.log('stdout: ' + stdout);
console.log('stderr: ' + stderr);
if (error !== null) {
console.log('exec error: ' + error);
}
});
writeVal = 'squeezelite OFF';
}
});
v2.on('write', function(param) {
if (param[0] == '1') {
child = exec('sudo systemctl start shairport-sync',
function (error, stdout, stderr) {
console.log('stdout: ' + stdout);
console.log('stderr: ' + stderr);
if (error !== null) {
console.log('exec error: ' + error);
}
});
writeVal = 'shairport ON';
}
else if (param[0] == '0') {
child = exec('sudo systemctl stop shairport-sync',
function (error, stdout, stderr) {
console.log('stdout: ' + stdout);
console.log('stderr: ' + stderr);
if (error !== null) {
console.log('exec error: ' + error);
}
});
writeVal = 'shairport OFF';
}
});
v3.on('write', function(param) {
if (param[0] == '1') {
child = exec('ecasound -C -q -B:rt -b:1024 -f:16,2,48000 -i:alsahw,1,0',
function (error, stdout, stderr) {
console.log('stdout: ' + stdout);
console.log('stderr: ' + stderr);
if (error !== null) {
console.log('exec error: ' + error);
}
});
writeVal = 'analog ON';
}
else if (param[0] == '0') {
child = exec('sudo killall -15 ecasound',
function (error, stdout, stderr) {
console.log('stdout: ' + stdout);
console.log('stderr: ' + stderr);
if (error !== null) {
console.log('exec error: ' + error);
}
});
writeVal = 'analog OFF';
}
});
v0.on('read', function() {
v0.write(writeVal);
});