if(argc < 3) { perror("argc < 2"); return -1; }

   int fdin1 = open(argv[1],O_RDONLY,S_IREAD);
   if(fdin1 == -1) { perror("fdin1 == -1"); return -1; }

   int fdin2 = open(argv[2],O_RDONLY,S_IREAD);
   if(fdin1 == -1) { perror("fdin2 == -1"); return -1; }

   char buf1[1024],buf2[1024];
   int r,s,flag=0,nLine=1;

   r = readln1(fdin1,buf1,1024);
   s = readln1(fdin2,buf2,1024);

   if(r==0 || s==0)
   {
      char sChar[10];
      int sizeChar = intToString(sChar,1);

      char sLine[10];
      int sizeLine = intToString(sLine,1);

      write(1,argv[1],strlen(argv[1]));
      write(1," ",1);
      write(1,argv[2],strlen(argv[2]));
      write(1,": char ",7);
      write(1,sChar,sizeChar);
      write(1,", line ",7);
      write(1,sLine,sizeLine);
      write(1,"\n",1);
      return EXIT_SUCCESS;
   }

   while(r>0 && s>0 && flag == 0)
   {
      int i,n;

      if(r<s) n=r;
      else n=s;

      for(i=0; i<n; i++)
      {
         if(buf1[i] != buf2[i])
         {
            char sChar[10];
            int sizeChar = intToString(sChar,i+1);

            char sLine[10];
            int sizeLine = intToString(sLine,nLine);

            write(1,argv[1],strlen(argv[1]));
            write(1," ",1);
            write(1,argv[2],strlen(argv[2]));
            write(1,": char ",7);
            write(1,sChar,sizeChar);
            write(1,", line ",7);
            write(1,sLine,sizeLine);
            write(1,"\n",1);
            flag = 1;
            break;
         }
         else
         {
            r = readln1(fdin1,buf1,1024);
            s = readln1(fdin2,buf2,1024);
         }
      }

      nLine++;
   }