SD card file exists problem

Hi.

I have a problem that I want to check a file is existing in SD card or not. I just creat a file name test.txt in a folder named bin in SD card. However, my program cannot find it. So, can anyone tell me what’s wrong with my code?

Thanks.

#include <Process.h>
#include <Bridge.h>
#include <FileIO.h>
#include <stdio.h>

void setup() {
 Serial.begin(9600);
 delay(5000);
 Bridge.begin();
 FileSystem.begin();
 boolean x = FileSystem.exists("/mnt/sda1/fmbk_ctrl.sh");
 Serial.println(x);
}

void loop() {

}

I just creat a file name test.txt in a folder named bin in SD card. However, my program cannot find it. So, can anyone tell me what's wrong with my code?

Is that a trick question? You are NOT looking for test.txt in a directory named bin.