File Write Script
This example writes to a file using the FileIO classes into the Yún device's filesystem. A shell script file is created in /tmp, and is executed afterwards.
Circuit
Code
Include the FileIO header, for communicating with the filesystem.
#include <FileIO.h>
In setup()
, initialize Bridge, Serial communication, and FileSystem. Wait for an active serial connection, and call a custom function uploadScript()
which will upload your file, before starting loop()
.
void setup() {
Bridge.begin();
Serial.begin(9600);
while(!Serial); // wait for Serial port to connect.
Serial.println("File Write Script example\n\n");
FileSystem.begin();
uploadScript();
}
loop()
will just execute your script every 5 seconds by calling another custom function, runScript()
.
void loop() {
runScript();
delay(5000);
}
Your uploadScript()
function will create a shell script in the Linux file system that will check the network traffic of the WiFi interface. Create the file and open it by creating an instance of the File@ class, and calling
FileSystem.open()@@ indicating where you would like to create the script. You'll store the script in "/tmp", which resides in RAM, to preserve the limited number of FLASH memory read/write cycles.
void uploadScript() {
File script = FileSystem.open("/tmp/wlan-stats.sh", FILE_WRITE);
Write the contents of the script to the file with File.print()
. begin by printing the header, "#!/bin/s", then the utility ifconfig
. @ifconfig@ is a command line utility for controlling network interfaces. you'll be looking at the WiFi interface, which is referred to as "wlan0". The utility grep
will search the output of ifconfig
. You're looking for the number of bytes received , so search for the keywords "RX bytes" and close the file.
script.print("#!/bin/sh\n");
script.print("ifconfig wlan0 | grep 'RX bytes'\n");
script.close(); // close the file
Instantiate a Process to make the script executable. chmod@ is a command that will change the modes of files. By sending the
chmod@@ command and filepath, you can make your shell script run like an application.
Process chmod;
chmod.begin("chmod"); // chmod: change mode
chmod.addParameter("+x"); // x stays for executable
chmod.addParameter("/tmp/wlan-stats.sh");
chmod.run();
}
The runScript()
function will create a Process that runs the script and prints the results to the Serial Monitor. Create a named Process, and start your script by calling Process.begin(filepath)
and Process.run()
.
void runScript() {
Process myscript;
myscript.begin("/tmp/wlan-stats.sh");
myscript.run();
Create a string to hold the output, and read the output into it
String output = "";
while (myscript.available()) {
output += (char)myscript.read();
}
Remove the blank spaces at the beginning and end of the string and print it to the serial monitor :
output.trim();
Serial.println(output);
Serial.flush();
}
The complete sketch is below :
/*
Write to file using FileIO classes.
This sketch demonstrate how to write file into the YunShield/Yún filesystem.
A shell script file is created in /tmp, and it is executed afterwards.
created 7 June 2010
by Cristian Maglie
This example code is in the public domain.
http://www.arduino.cc/en/Tutorial/FileWriteScript
*/
#include <FileIO.h>
void setup() {
// Setup Bridge (needed every time we communicate with the Arduino Yún)
Bridge.begin();
// Initialize the Serial
SerialUSB.begin(9600);
while (!SerialUSB); // wait for Serial port to connect.
SerialUSB.println("File Write Script example\n\n");
// Setup File IO
FileSystem.begin();
// Upload script used to gain network statistics
uploadScript();
}
void loop() {
// Run stats script every 5 secs.
runScript();
delay(5000);
}
// this function creates a file into the linux processor that contains a shell script
// to check the network traffic of the WiFi interface
void uploadScript() {
// Write our shell script in /tmp
// Using /tmp stores the script in RAM this way we can preserve
// the limited amount of FLASH erase/write cycles
File script = FileSystem.open("/tmp/wlan-stats.sh", FILE_WRITE);
// Shell script header
script.print("#!/bin/sh\n");
// shell commands:
// ifconfig: is a command line utility for controlling the network interfaces.
// wlan0 is the interface we want to query
// grep: search inside the output of the ifconfig command the "RX bytes" keyword
// and extract the line that contains it
script.print("ifconfig wlan0 | grep 'RX bytes'\n");
script.close(); // close the file
// Make the script executable
Process chmod;
chmod.begin("chmod"); // chmod: change mode
chmod.addParameter("+x"); // x stays for executable
chmod.addParameter("/tmp/wlan-stats.sh"); // path to the file to make it executable
chmod.run();
}
// this function run the script and read the output data
void runScript() {
// Run the script and show results on the Serial
Process myscript;
myscript.begin("/tmp/wlan-stats.sh");
myscript.run();
String output = "";
// read the output of the script
while (myscript.available()) {
output += (char)myscript.read();
}
// remove the blank spaces at the beginning and the ending of the string
output.trim();
SerialUSB.println(output);
SerialUSB.flush();
}
See Also
- Bridge Library - Your reference to the Bridge Library
- Bridge – Simple REST style calls to access analog and digital pins
- Console Ascii Table – A complete ASCII table printed to the Console
- Console Pixel – Turn an LED on and off through the Console
- Console Read - Read data coming from bridge using the Console.read() function
- Data Logger - Log data from three analog sensors to an SD card.
- Http Client - A basic HTTP client that connects to the internet and downloads content.
- Http Client Console - HTTP client that connects, downloads content and shows it using WiFi and Console.
- Mailbox Read Message - How to read the messages queue, called Mailbox, using the Bridge library.
- Process - How to run linux processes using an Yún.
- Remote Due Blink - How to upload remotely a sketch on DUE boards.
- Shell Commands - How to run linux shell commands using a Yún.
- Temperature Web Panel - How to serve data from an analog input via the Yún's built-in webserver.
- Time check - Gets the time from Linux via Bridge then parses out hours, minutes and seconds.
- WiFi Status - Prints information about the status of your wifi connection.
- Yún First Configuration - Easily configure your Yún device using Serial Monitor and USB port.
- Serial Terminal - Use the Yún's 32U4 processor as a serial terminal for the Linux side on the Yún.
Last revision 2016/05/25 by SM