exec

Overview

The exec node runs operating system commands from within your EdgeFlow pipeline. It supports both one-shot execution and long-running spawned processes, with configurable timeouts. Cross-platform compatible — uses sh -c on Linux/macOS and cmd /C on Windows.

Properties

Execution Modes

command: "uname -a"
// Waits for command to finish
// Output 1: stdout (string)
// Output 2: stderr (string)
// Output 3: return code (number)

command: "tail -f /var/log/syslog"
useSpawn: true
// Output streams in real-time
// Each line → separate message
// msg.payload contains each line

// Executed as:
sh -c "your_command_here"

// Pipes and redirects work:
command: "ps aux | grep node"

// Executed as:
cmd /C "your_command_here"

// Windows commands:
command: "systeminfo"

Example: System Information Gathering

Collect host system details and disk usage for monitoring dashboards.

// Exec node configuration — hostname and OS info
{
  "command": "uname -a",
  "appendPayload": false,
  "useSpawn": false,
  "timeout": 10
}

// Output 1 (stdout):
// "Linux edgeflow-pi 5.15.0 #1 SMP armv7l GNU/Linux"

// Second exec node — disk usage
{
  "command": "df -h --output=target,pcent | tail -n +2",
  "timeout": 10
}

// Output 1 (stdout):
// "/              45%"
// "/boot          12%"
// "/data          78%"

// Chain into a function node to parse and alert if > 80%

Example: GPIO Control via Command Line

Toggle a Raspberry Pi GPIO pin using the command-line sysfs interface.

// Exec node — export and set GPIO pin high
{
  "command": "echo 17 > /sys/class/gpio/export 2>/dev/null; echo out > /sys/class/gpio/gpio17/direction; echo 1 > /sys/class/gpio/gpio17/value",
  "timeout": 5
}

// Exec node — read GPIO pin state
{
  "command": "cat /sys/class/gpio/gpio17/value",
  "timeout": 5
}

// Output 1 (stdout): "1"  (pin is HIGH)

// Use appendPayload to pass dynamic pin numbers:
{
  "command": "echo",
  "appendPayload": true
}
// msg.payload = "1 > /sys/class/gpio/gpio17/value"
// Effectively runs: echo 1 > /sys/class/gpio/gpio17/value

Example: Dynamic Command with Payload

Ping a host address supplied by the incoming message payload.

// Exec node configuration
{
  "command": "ping -c 3",
  "appendPayload": true,
  "timeout": 15
}

// Incoming message
{
  "payload": "192.168.1.1"
}

// Executes: ping -c 3 192.168.1.1
// stdout → "3 packets transmitted, 3 received, 0% packet loss"
// return code → 0 (success)

Common Use Cases