Hi there, The following code is part of a little program I wrote to compare two similar files byte for byte. The job of this part is to get the length of a file.

int n_BYTE1 = 0; // <-- this int holds the length of the file
FILE *stream1;


// get length of files
	do {
		fgetc(stream1);
		n_BYTE1++;
	} while (feof(stream1) == 0);
	n_BYTE1--;
	rewind(stream1); 
  

The problems is this seems to work only for relatively small files. Whenever I try to use it on a larger file (170 kB for example) it returns an incorrect filesize. Usually the filesize I get is WAY too small. I have had the program tell me that a 340kB file has in fact a size of only 1010 bytes! :confused: Could it be that there is a byte somwhere in these large files that the program interprets as the EOF?? Help me out, please. I'm lost. Thanks in advance. Regards, Markus Edited by - Red Ant on August 3, 2001 8:50:16 AM

The typical way to get the size of a file is to use the C library function stat: (put a less than and greater than around the include filename...)

#include sys/stat.h
...
struct stat results;

if (stat("input.bin", &results) == 0)
// The size of the file in bytes is in
// results.st_size
else
// An error occurred


Edited by - kingy on August 3, 2001 8:57:50 AM

Thanks a million!!! Works like a charm.

Thanks again for your help. However, I just noticed that even though I now get the correct size of the file, the same problem continues to bug me in another part of the program.

// This loop is suppose to run through both files and compare them byte for byte. If any differences are found they are stored in an array.for (ADDRESS = 0; ADDRESS < n_READ_to; ADDRESS++)	{		c_BYTE1 = (char)fgetc(stream1);		c_BYTE2 = (char)fgetc(stream2);		if (c_BYTE1 != c_BYTE2)		{			DIFF_ofs[index] = offset;			DIFF_B1[index]  = c_BYTE1; 			DIFF_B2[index]  = c_BYTE2;			index++;		}		offset++;	} 

The problem is the same as before. The program just won''t read large files to the end but instead reads only ''till the 1010th or so byte. Is the function I use to read the file not suitable for large files? What function would you guys use to read large files? Thanks again for your patience.

Markus

Thanks again for your help. However, I just noticed that even though I now get the correct size of the file, the same problem continues to bug me in another part of the program.

// This loop is suppose to run through both files and compare them byte for byte. If any differences are found they are stored in an array.for (ADDRESS = 0; ADDRESS < n_READ_to; ADDRESS++)	{		c_BYTE1 = (char)fgetc(stream1);		c_BYTE2 = (char)fgetc(stream2);		if (c_BYTE1 != c_BYTE2)		{			DIFF_ofs[index] = offset;			DIFF_B1[index]  = c_BYTE1; 			DIFF_B2[index]  = c_BYTE2;			index++;		}		offset++;	} 

The problem is the same as before. The program just won''t read large files to the end but instead reads only ''till the 1010th or so byte. Is the function I use to read the file not suitable for large files? What function would you guys use to read large files? Thanks again for your patience.

Markus

1. What mode did you open both files in ? For this both should really be opened as binary: fopen("blah.bin", "rb")

2. What are the data types of ADDRESS and n_READ_to, they should be at least int.

3. Where does the value of n_READ_to come from ? It should be the size of the smallest of the two files.

4. How big are the DIFF_offs, DIFF_B1 and DIFF_B2 arrays ? If they aren''t big enough to hold n_READ_to elements, you could end up overwriting the end of the array, which can cause very hard to trace crashes and other random problems.

--
Simon O''''Connor
Creative Asylum Ltd
www.creative-asylum.com

This forum rocks! You guys have solved all my problems. Everything works as it should now.

S1CA, I had opened both files in read only mode (fopen("bla.txt","r"). That seems to have been the problem. I did as you told me and opened in binary mode (rb) and now it works perfectly! Many thanks! See ya!

Markus