[SOLVED] Arduino Yún: Sketch to create unique filename

Official Hardware Classic Yún
1

Hallo all,

I'm trying to do something that seems to me as rather simple, but I'm struggling to make it work.
The sketch should write a file to the Linux machine, where it will be handled by a Python script that will delete the file when it's done. To prevent the file to be overwritten every now and than, I want to generate a rather unique filename using for instance the millis() function. This turns over ever 50 days or so, and this should be more than enough.

What I tried to do is something like this:

void SendToPython(){
  Process p;

  char t[] = {millis()};  // Should be used to make the filename unique, 
                          // by replacing 'TestFile' with this number.

  char f[] = {"/SPOOL/INPUT/msg_TestFile.txt"};

  // Create a new file
  Serial.println("Creating file");
  File dataFile = FileSystem.open(f , FILE_WRITE);
  if (dataFile) {
      dataFile.print("Write some string to the file");
    }
    dataFile.close();
  }  
  else { // if the file isn't open, pop up an error:
    Serial.println("Error opening messagefile in '/SPOOL/INPUT/'");
  } 

  // Ensure the last bit of data is sent.
  Serial.flush();
  Serial.println("__________________________end message____________________________ ");
}

As long as I create the file with the char-string as I do above, all is fine.
When I try to insert the value of millis() into the string, in all possible ways I could imagine, I keep getting conversion errors.

How could I handle this the best please?

Friendly greetings,
Rens

2

Posting code that doesn't do what you want and doesn't produce an error does nothing. Without an error it is hard to imagine what "all possible ways I could imagine" would be.

Make the simplest example that produces a conversion error and you think should give you what you want and someone may be able to help.

3

You could use sprintf when to create the file name.
For example

char newfile[50];
sprintf(newfile, "/mnt/sd/File%04d.txt", millis());

Or use an increasing number like this:

http://forum.arduino.cc/index.php?topic=204750.msg1507809#msg1507809

4

Erni:
You could use sprintf when to create the file name.
For example

char newfile[50];

sprintf(newfile, "/mnt/sd/File%04d.txt", millis());

This did the trick for me.
Thank you very much. :slight_smile:

5

And a liiiiitle bit better:

char newfile[50];
sprintf(newfile, "/mnt/sd/File%04u.txt", millis());

Otherwise I get a filename like "File-8723.txt" every now and then.