Every programmer, regardless of the language in use, should write his/her own hex viewer, right? Well, this is mine. Years ago whenever I taught someone the C language, this was my damn favourite. And still, it's useful whenever I do some reverse engineering on Microsoft Excel file format.

It should compile in any platform. And just for the sake of completeness, building it using gcc 3.3 (Linux), plus additional compression with UPX, gives less than 7 KB executable file. Enjoy!

#include <stdio.h>

int main( int argc, char** argv )
{
  FILE *f;
  unsigned char buf[16];
  int i, j, k;

  if( argc < 2 ) return 0;
  f = fopen( argv[1], "rb" );
  if( !f ) perror( "error" );
  else
  {
    k = 0;
    while( !feof( f ) )
    {
      j = fread( buf, 1, 16, f );
      printf("%08x   ", k ); k += j;
      for( i = 0; i < 16; i++ )
        if( i < j ) printf("%02x ", buf[i] ); else printf("   ");
      printf("    ");
      for( i = 0; i < 16; i++ )
        if( i < j ) printf("%c", (buf[i] > 31) ? buf[i] : '.'); 
          else printf("   ");
      printf("\n");
    }
    fclose( f );
  } 
  return 0;
}

- posted by Ariya Hidayat @ 9:49 AM