process-shell.ino
The Process class is the sketch's remote shell: cat /proc/loadavg gives the Linux load, SoC temperature completes the picture. The MCU supervises the system beside it, in ten lines.
Hardware
An Arduino Yun (ATmega32U4 + Linino Linux on an Atheros AR9331, Wi-Fi and Ethernet, microSD slot). No external component.
Wiring
Nothing to wire; the USB serial monitor shows the results.
How it works
runShellCommand runs the command in the Linux through the bridge daemon; readString reads stdout until the process ends. running() acts as a synchronization barrier.
Running it
Arduino IDE: select the serial port to upload, then the Arduino Yun board for the monitor. Linux side: ssh root@arduino.local (distribution password). The Yunwizard app configures the network.
Variants
runShellCommandAsynchronously + callback to avoid blocking, or write to a Linux file with FileIO for logging.
process-shell.ino
// Process : le croquis lance une commande Linux et recupere la sortie.
#include <Bridge.h>
#include <Process.h>
void setup() {
Bridge.begin();
Serial.begin(9600);
while (!Serial);
}
void loop() {
Process charge;
charge.runShellCommand("cat /proc/loadavg");
String ligne = charge.readString(); // 1re ligne = charge 1/5/15 min
while (charge.running()); // attend la fin du flux
Serial.print("charge systeme : ");
Serial.println(ligne);
// Autre exemple : temperature du SoC (varie selon la distribution)
Process temp;
temp.runShellCommand("cat /sys/class/thermal/thermal_zone0/temp 2>/dev/null");
String t = temp.readString();
while (temp.running());
if (t.length() > 4) {
Serial.print("SoC : ");
Serial.println(t.toFloat() / 1000.0);
}
delay(5000);
}