Thread: binary file again

Hi all,

I need to read a binary file as a string and store it into a buffer to do some stuff, but when i run my program i got some strange characters.

Here is my program:

Code:

#include <stdio.h>
#include <stdlib.h>

int
main (int argc, char **argv)
{
   FILE                *in;
   char                head_string[5];
   int                 j;
   char                buffer[512];

   in = fopen(argv[1], "rb");

   if(in == NULL) {
       fprintf (stderr, "Can't open file.\n");
       return EXIT_FAILURE;
   }

   while (fgets(buffer, sizeof(buffer), in) != NULL) {
       for (j = 0; j < 5 ; j++)
               head_string[j] = buffer[j];
       printf("The length of the block is : %s\n", head_string);         
   }          

   fclose(in);

   return 0;
}

When i run my program (passing a binary file as a parameter) i got a strange chars:

Code:

$ ./a.out log_dump.data
The length of the header is : )
The length of the header is : ????
The length of the header is : S%a0
The length of the header is : ?????
The length of the header is : ?????
The length of the header is : ?????
The length of the header is : ?????
The length of the header is : ?????
The length of the header is : ?????
The length of the header is : ?????
The length of the header is : ?????
The length of the header is : ?????
The length of the header is : ?????
The length of the header is : ?????
The length of the header is : ?????
The length of the header is : ?????
The length of the header is : )
The length of the header is : ????
The length of the header is : SF0i

the display of my file using an hex dump:

Code:

0500    0033    5100    f100    ffff    00ff    0000    0000
0000    0000    0000    0000    0000    0000    0001    ffff
ffff    ffff    ffff    ffff    ffff    00ff    00ff    0500
f008    ff01    f008    ff01    0002    4233    0219    0912
ff20    5343    5049    3130    2020    ffff    ffff    ffff
ffff    0506    2926    0007    fff0    ffff    ffff    ffff
0000    4900    0101    2122    0000    4900    328a    ca41
0002    0033    5100    f100    ffff    ffff    0000    4200
2117    0100    1400    53f2    6125    0030    3921    33f0
9371    7372    fff2    ffff    00ff    4207    2117    0100
1400    53f8    4606    6930    9477    06f0    9371    9372

Thanks for your help.

Don't use fgets() for binary data. Use fread() (and fwrite() if needed).

Thanks for the reply, but if i use fread i got the same output:
fread(buffer, sizeof(buffer), 1, in).

Thanks.

I don't understand your fread() statement:

Code:

//or in this case, your fread():
fread(buffer, sizeof(buffer), 1, in).

That would try to read in the whole buffer size, with every read. I doubt that is what you want. Try 5, instead.

fread(buffer, sizeOfTheItemYouWantToRead, Number of ItemsYouWantPerRead, in)

Thanks Adak,

With your fread, i have a bus error and the same output as before!
My file is 4k and i want to split it to 8 buffers of size 512 Bytes each to do some parsing. that's why i'm trying to read my whole buffer size.

Ragards.

Agrr Have you tried to use debugger yet?
printf() for binary input is not going to work. %s needs C style string.(null terminated char array).
Your data may have null byte also.

Thanks all,

your answers will not change anything! i think that the problem come from the formatting of readed data in the binary file.

Ragrds.

Post up your binary file on Swoopshare and give us a link to it, and I GUARANTEE our answers will change what's happening.

We just can't give you exactly the answers you want/need, without having the file.

adak, write to stdin?

you can download the binary file here:

file_data - 4shared.com - online file sharing and storage - download

Thanks.

Originally Posted by Bayint Naung

adak, write to stdin?

Ha ha - that was a TEST to see if you were awake!!

I am barely awake and will edit that to avoid confusion - thanks.

in message 1 it was just a sample! what this will really change in the final solution? it's just a binary data.

Regards.

Originally Posted by jean.yves

in message 1 it was just a sample! what this will really change in the final solution? it's just a binary data.

Regards.

Why do you think the first few bytes indicate the length of the data?