datalogger without SD card?

is it possible to save data to a txt file, like a datalogger example, without SD card?
I need to save the data in a small txt file in the internal memory of the yun.
And is it possible to read this data from another arduino like http client example?

Anyone can help me?

You could save it at /tmp/ directory( in RAM) , but once power off then it will lost. could use cron copy the content of it hourly.

sonnyyu:
You could save it at /tmp/ directory( in RAM) , but once power off then it will lost. could use cron copy the content of it hourly.

where is the /tmp/ directory?
is it possible to view it in the browser?
and is it possible to open and modify the file in /tmp/ from another arduino in the same network?

touch /tmp/datalog.txt

Change from:

File dataFile = FileSystem.open("/mnt/sd/datalog.txt", FILE_APPEND);

to:

File dataFile = FileSystem.open("/tmp/datalog.txt", FILE_APPEND);

Open and modify the file via file share (Samba/Cifs)

Server:

http://forum.arduino.cc/index.php?topic=221286.msg1608036#msg1608036

Client:

http://forum.arduino.cc/index.php?topic=210753.0

http://playground.arduino.cc/Hardware/Yun#Mounting_cifs_drive

sonnyyu:

touch /tmp/datalog.txt

Change from:

File dataFile = FileSystem.open("/mnt/sd/datalog.txt", FILE_APPEND);

to:

File dataFile = FileSystem.open("/tmp/datalog.txt", FILE_APPEND);

Open and modify the file via file share (Samba/Cifs)

Server:

Samba on Yun - Arduino Yún - Arduino Forum

Client:

[SOLVED] Fail to mount cif drive - Arduino Yún - Arduino Forum

Arduino Playground - HomePage

Thanks sonny, but if I follow your links I need the SD card inserted in the yun.
Do you know another method for read txt file in/tmp/ from another arduino or computer?

I think what you are searching for are these packages:

openssh-sftp-server
openssh-sftp-client

(both installable via SSH, opkg install ... or via the Luci-Interface of the Yun)

I use openssh-sftp-server, so that I can remotely see all files of my yun (via "Cyberduck", a sftp-app for MacOSX ).

If you install those both packages on both Arduinos, then one of them should be
able to establish a connection as a client (Arduino Nr.1) to the server (Arduino Nr.2)...

But I don't know the code for establishing that connection (must be documented somewhere on the openssh-sftp-creators website)....
BUT I'd love to read them, if you figure it out !! I also need that kind of connection!

/*
  SD card datalogger

 This example shows how to log data from three analog sensors
 to an SD card mounted on the Arduino Yún using the Bridge library.

 The circuit:
 * analog sensors on analog pins 0, 1 and 2
 * SD card attached to SD card slot of the Arduino Yún

 Prepare your SD card creating an empty folder in the SD root
 named "arduino". This will ensure that the Yún will create a link
 to the SD to the "/mnt/sd" path.

 You can remove the SD card while the Linux and the
 sketch are running but be careful not to remove it while
 the system is writing to it.

 created  24 Nov 2010
 modified 9 Apr 2012
 by Tom Igoe
 adapted to the Yún Bridge library 20 Jun 2013
 by Federico Vanzati
 modified  21 Jun 2013
 by Tom Igoe

 This example code is in the public domain.

 http://arduino.cc/en/Tutorial/YunDatalogger

 */

#include <FileIO.h>

void setup() {
  // Initialize the Bridge and the Serial
  Bridge.begin();
  Serial.begin(9600);
  FileSystem.begin();

  while (!Serial); // wait for Serial port to connect.
  Serial.println("Filesystem datalogger\n");
}


void loop () {
  // make a string that start with a timestamp for assembling the data to log:
  String dataString;
  dataString += getTimeStamp();
  dataString += " = ";

  // read three sensors and append to the string:
  for (int analogPin = 0; analogPin < 3; analogPin++) {
    int sensor = analogRead(analogPin);
    dataString += String(sensor);
    if (analogPin < 2) {
      dataString += ",";  // separate the values with a comma
    }
  }

  // open the file. note that only one file can be open at a time,
  // so you have to close this one before opening another.
  // The FileSystem card is mounted at the following "/mnt/FileSystema1"
 // File dataFile = FileSystem.open("/mnt/sd/datalog.txt", FILE_APPEND);
File dataFile = FileSystem.open("/tmp/datalog.txt", FILE_APPEND);
  // if the file is available, write to it:
  if (dataFile) {
    dataFile.println(dataString);
    dataFile.close();
    // print to the serial port too:
    Serial.println(dataString);
  }
  // if the file isn't open, pop up an error:
  else {
    Serial.println("error opening datalog.txt");
  }

  delay(15000);

}

// This function return a string with the time stamp
String getTimeStamp() {
  String result;
  Process time;
  // date is a command line utility to get the date and the time
  // in different formats depending on the additional parameter
  time.begin("date");
  time.addParameter("+%D-%T");  // parameters: D for the complete date mm/dd/yy
  //             T for the time hh:mm:ss
  time.run();  // run the command

  // read the output of the command
  while (time.available() > 0) {
    char c = time.read();
    if (c != '\n')
      result += c;
  }

  return result;
}

run

touch /tmp/datalog.txt

at linino console first.