what not to use C for

#include <stdio.h>
#include <string.h>

int main(int argc, char **argv)
{
  FILE *f = fopen(argv[1], "r");
  int i = 0;
  int c = EOF;
  char buffer[20];
  char filename[255];
  FILE *o = NULL;
  fread(buffer, 1, 20, f);
  while((c = fgetc(f)) != EOF)
  {
    if(!memcmp(buffer, "\xff\xd8\xff\xe1" "5\xfe" "Exif", 10))
    {
      if(o != NULL)
        fclose(o);
      snprintf(filename, 255, "%i.%s", i++, argv[2]);
      o = fopen(filename, "w");
    }
    fputc(*buffer, o);
    memmove(buffer, buffer+1, 19);
    buffer[19] = c;
  }
  fwrite(buffer, 1, 20, o);
  fclose(o);
  fclose(f);
}