reading file from offset in c

[coder_10]

I am trying to read a file from an offset till end of file:

int i,sizeb=210;
char *buffer;  //[1024];
FILE *f;


f = fopen("myfile", "rb");

printf("Reading file.\n");

fseek(f, sizeb, SEEK_SET);
long s = ftell(f);
//rewind(f);

fread(buffer, s, 1, f);
fclose(f);

But I never get the right result.

Also when I use a large buffer like buffer[10240000] it wil crash immediately upon running it.

Maybe someone can help me fix it.

[rubberman]

The large buffer is causing you to crash because it is being allocated on the stack and you don't have enough stack space. If this is Linux/Unix you can fix that with the system ulimit command, unless the sysadmin has restricted you in some way. In any case, this is non-functional code. What does the char* buffer point to? So, you are seeking 210 bytes into the file, and have commented out rewind(), and then read 240 bytes, but it would start there and not at the beginning of the file. So, create a buffer of some reasonable size (up to 1MB may be ok - you are using 10M, and most systems limit stack to 8M or less), seek to the position that you want to start at, and then start reading in a loop until you get to feof(f). If you want to read it all into one buffer, then allocate buffer on the heap using malloc/calloc function calls.

If you want to know where the end of the file may be in bytes from the beginning, then try using fseek(f, 0L, SEEK_END), then ftell(). That will tell you just how much buffer space you need.

[coder_10]

Could you write that out in code?

And the idea is to start reading from offset 210 till the end of the file. Not from the beginning.

I tried 1mb buffer size but than it crashes. But regardless, what if my file is larger than 1mb, what than?