Getting MAC address in c and writing it to a txt file - c

Question

Following is my code. In this program I use system function and passe a command line argument to get the mac address of the pc and then write it into the txt file. txt file is creating successfully. But When I try to open the txt file which was created it wont show anything. It show letter M and some blank spaces. Any idea why is this happening ? Thank you.
#include<stdio.h>
int main()
{
system("wmic nic where (AdapterTypeId=0 AND netConnectionStatus=2) get MACAddress >macaddress.txt");
FILE * fpointer=fopen("macaddress.txt","r");
char buffer[500];
while(!feof(fpointer)){
fgets(buffer,500,fpointer);
puts(buffer);
}
fclose(fpointer);
}

Answer 1

This will do what you want, but if instead of just printing the contents of the file you actually want to do something with it and you need the text as ASCII you'll need to perform that conversion yourself from wide characters.
Since this particular file is just normal letters and numbers text you can convert the wide string to narrow with sprintf.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
system("wmic nic where (AdapterTypeId=0 AND netConnectionStatus=2) get MACAddress > macaddress.txt");
//Binary mode tells fgetws to read wide characters instead of multi-byte.
FILE * fp = fopen("macaddress.txt", "rb");
if (fp)
{
wchar_t buffer[500] = { 0 };
fread(buffer, 1, 2, fp); //read and discard BOM
while (fgetws(buffer, 500, fp))
{
// %ls means the parameter is a wide string.
// %S also works in Visual Studio
printf("%ls", buffer);
//Convert wide characters to ASCII
//This assumes the wide characters are all in the ASCII range
char ascii[500] = { 0 };
sprintf(ascii, "%ls", buffer);
printf("%s", ascii);
}
fclose(fp);
}
return 0;
}

Answer 2

It is not an ASCII encoded file. Here is a dump
0 1 2 3 4 5 6 7 8 9 A B C D E F
0000:0000 FF FE 4D 00 41 00 43 00 41 00 64 00 64 00 72 00  ■M.A.C.A.d.d.r.
0000:0010 65 00 73 00 73 00 20 00 20 00 20 00 20 00 20 00 e.s.s. . . . . .
0000:0020 20 00 20 00 20 00 20 00 0D 00 0A 00
etc so as not to reveal my MAC address.
Note too it contains zeros which will terminate any string output after reading with fgets.
My text editor (Notepad++) shows the correct content because it sets the right text format automatically.