file read using fgetc adds FF at the end - system-verilog

Question

I'm reading a file using fgetc. File reading starts at an offset.At the end I see 8'hFF getting appended at the end of file.I'm expecting 6 bytes in the file but see 7 in them.I'm not sure why this is happening. Any ideas?
Below is my code:
module file_read();
integer fd,fd1,file_char,status;
logic [7:0] captured_data;
initial begin
fd = $fopen("input_file", "rb");
fd1 =$fopen("write_file","w");
status=$fseek(fd,1872,0);
assert (status);
// while ($fgetc(fd) != `EOF) begin
while (!$feof(fd)) begin
file_char=$fgetc(fd);
$display("file char is %h",file_char);
end
end // initial begin
Below are the file contents(in hex):
last line of input_file(total file size =1878):
0000750: 0000 1567 d48d ...g..
write_file:
0000000: 0000 1567 d48d ff ...g...
Thanks!

Answer 1

The reason you are getting the extra 'hff at the end of the written file is due to how $feof (or generally the foef C function) works. Simply put, it doesn't check if the next read is off the end of the file but if the previous read read off the end of the file. So, if you are reading character by character (byte by byte) using $fgetc, $feof will only return true once $fgetc reads off the end of the file, and returns EOF itself (ie, -1 or 'hff if converted to logic [7:0]). You should be checking for this error condition each time you read a byte, something like this:
integer fd, ch;
...
fd = $fopen("file.bin", "rb");
...
while ((ch = $fgetc(fd)) != -1) begin
$display(ch);
end