Problem on creating new files using SD library

Projects Programming
1

Hi, I came across a problem on creating new files into SD card using SD library.

What I want to do is every time the device turns on it will create a new file with a unique name in the SD card. So I used Unix time as the name of the file. But it won't work, nothing will be created in the SD card and I think this may be caused by the length of Unix time which contains 10 numbers, such as 1559836353.csv.
If I use a number with only 8 numbers, such as 12345678.csv, then everything just works well.

Here is my code related to this problem.

#include <SD.h>
#include <DS3231.h>

File mySensorData;
static String filename;

void setup(){
  pinMode(10, OUTPUT);
  SD.begin(10); 
  rtc.begin();

  filename = String(rtc.getUnixTime(rtc.getTime())) + ".csv";
  // filename = "12345678.csv"; this line will work.
  mySensorData = SD.open(filename, FILE_WRITE);
  mySensorData.close();
}

void loop(){
// other functions
}

So I want to know if there is any solution to this problem or if there are some other methods to create a file with a unique name which only contains less than 8 characters.

Thanks a lot!

2

I think this may be caused by the length of Unix time which contains 10 numbers

The SD library only supports 8.3 format filenames

3

Thanks for your help!
Oh, that's so bad...
Do you have any ideas about any other things we can use as a unique name which suits for this situation?
Thank you very much!

4

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5

Thanks for your reply!

Good idea! I have thought about this. The only flaw about it is that the last 8 digits will run out within about 3 years, which is not a big problem though.

A few minutes ago, I just realized that I could first create a folder using the current month as its name, like 2019-Jun. Then I can use day hours minutes and seconds as the file names, like "ddhhmmss", which may make more sense to most people.

Thank you so much!