output file name

Comments

• MT2002

  May 2007

  : How do I create an output file name using some of the values I have
  : in an array?
  :
  : normally,
  :
  : FILE *wt;
  : wt = fopen ("outputfile", "w");
  : fprintf ...
  : fclose(wt);
  :
  : so what I want is, instead of me specifying a name such as, the
  : "outputfile", I want the program to get the name combining some
  : values I have in an array.
  :
  : pls help me... and thanks in advance..
  :
  
  Derefrence the array through its index:
  
  [code]
  FILE *wt;
  [b]wt = fopen (names[0], "w");[/b]
  fprintf ...
  fclose(wt);
  [/code]
• mathy

  June 2007

  : : How do I create an output file name using some of the values I have
  : : in an array?
  : :
  : : normally,
  : :
  : : FILE *wt;
  : : wt = fopen ("outputfile", "w");
  : : fprintf ...
  : : fclose(wt);
  : :
  : : so what I want is, instead of me specifying a name such as, the
  : : "outputfile", I want the program to get the name combining some
  : : values I have in an array.
  : :
  : : pls help me... and thanks in advance..
  : :
  :
  : Derefrence the array through its index:
  :
  : [code]:
  : FILE *wt;
  : [b]wt = fopen (names[0], "w");[/b]
  : fprintf ...
  : fclose(wt);
  : [/code]:
  
  
  thanks for the help, but it doesn't seem to work fine. What I'm storing in my array is a bunch of numbers. so I want to combine those numbers to make a name for the output file.
  how do I do this?
  thanks alot!
  
• bilderbikkel

  June 2007

  From [[http://www.codepedia.com/1/CppIntToStr]]:
  
  #include
  #include
  
  //Converts an int to std::string
  std::string itoa(const int x)
  {
  std::ostringstream o;
  if (!(o << x)) return "ERROR";
  return o.str();
  }
  
  
  int main()
  {
  const int myIndex = /*something*/ ;
  const std::string fileName = "MyFile" + itoa(myIndex) + ".txt";
  FILE * f = fopen(fileName.c_str(), "w");
  //...
  }
  [/code]
  
  
  bilderbikkel
• mathy

  June 2007

  : From [[http://www.codepedia.com/1/CppIntToStr]]:
  :
  : #include
  : #include
  :
  : //Converts an int to std::string
  : std::string itoa(const int x)
  : {
  : std::ostringstream o;
  : if (!(o << x)) return "ERROR";
  : return o.str();
  : }
  :
  :
  : int main()
  : {
  : const int myIndex = /*something*/ ;
  : const std::string fileName = "MyFile" + itoa(myIndex) + ".txt";
  : FILE * f = fopen(fileName.c_str(), "w");
  : //...
  : }
  : [/code]:
  :
  :
  : bilderbikkel
  
  
  sorry, but I do not understand this code. I'm trying to write this in C. Also I noticed itoa is not a std function. so pls help me to write this step by step.
  I think, I first have to get these numbers and concatenate them to make it as single integer. then cast it into string.
  here is what I have.
  
  int filename= year[0]+year[1];
  
  sprintf(some2, %d, filename);
  
  wt = fopen(some2, "w");
  
  I'm getting the following error messages.
  
  error: syntax error before
• bilderbikkel

  June 2007

  : : From [[http://www.codepedia.com/1/CppIntToStr]]:
  : :
  : : #include
  : : #include
  : :
  : : //Converts an int to std::string
  : : std::string itoa(const int x)
  : : {
  : : std::ostringstream o;
  : : if (!(o << x)) return "ERROR";
  : : return o.str();
  : : }
  : :
  : :
  : : int main()
  : : {
  : : const int myIndex = /*something*/ ;
  : : const std::string fileName = "MyFile" + itoa(myIndex) + ".txt";
  : : FILE * f = fopen(fileName.c_str(), "w");
  : : //...
  : : }
  : : [/code]: :
  : :
  : :
  : : bilderbikkel
  :
  :
  : sorry, but I do not understand this code. I'm trying to write this
  : in C. Also I noticed itoa is not a std function.
  There is no standard 'convert int to char*' function. That's why I GIVE you one called 'itoa', because there IS a standard function called 'atoi'.
  
  I do not know the C equivalent of 'itoa', but I've seen it in a C FAQ (try Google).
  
  : so pls help me to
  : write this step by step.
  : I think, I first have to get these numbers and concatenate them to
  : make it as single integer. then cast it into string.
  : here is what I have.
  :
  : int filename= year[0]+year[1];
  :
  : sprintf(some2, %d, filename);
  : wt = fopen(some2, "w");
  :
  : I'm getting the following error messages.
  :
  : error: syntax error before
• BitByBit_Thor

  June 2007

  
  : I believe in C you must use the standard function strcat. Other
  : people on this Board can help you with that. Or Google.
  :
  
  And some quotation marks around the %d to indicate it is a string ("%d") might help too.
  
  Best Regards,
  Richard
  
  The way I see it... Well, it's all pretty blurry
• mathy

  June 2007

  :
  : : I believe in C you must use the standard function strcat. Other
  : : people on this Board can help you with that. Or Google.
  : :
  :
  : And some quotation marks around the %d to indicate it is a string
  : ("%d") might help too.
  :
  : Best Regards,
  : Richard
  :
  : The way I see it... Well, it's all pretty blurry
  
  yes I fixed that but still its not giving out what I want.
  this is the array of int values I have...
  year[6]= 52
  year[7]=23
  
  so my output name should look like 5223.
  I thought sprintf would cast the int to string but it does not concatenate these values...
  any help <_>
  
  
  
• mathy

  June 2007

  : :
  : : : I believe in C you must use the standard function strcat. Other
  : : : people on this Board can help you with that. Or Google.
  : : :
  : :
  : : And some quotation marks around the %d to indicate it is a string
  : : ("%d") might help too.
  : :
  : : Best Regards,
  : : Richard
  : :
  : : The way I see it... Well, it's all pretty blurry
  :
  : yes I fixed that but still its not giving out what I want.
  : this is the array of int values I have...
  : year[6]= 52
  : year[7]=23
  :
  : so my output name should look like 5223.
  : I thought sprintf would cast the int to string but it does not
  : concatenate these values...
  : any help <_>
  :
  :
  :
  
  anyone?
  
• MT2002

  June 2007

  : anyone?
  
  You can use a combination of strcat() and sprintf().
  
  For example:
  [code]
  int pNum[MAX_INT] = {
  23,
  45,
  67
  };
  
  char* str = (char*)malloc(sizeof(int)*MAX_INT +1);
  int i=0;
  
  // insure we end in null terminator
  memset (str,0,sizeof(sizeof(int)*MAX_INT +1));
  
  // tedius method--convert int to string then concatenates it
  for (i=0; i<MAX_INT; i++) {
  
  char tmp[256];
  memset (tmp,0,256);
  sprintf (tmp, "%i", pNum[i]);
  strcat (str, tmp);
  }
  
  // print the string
  printf ("%s",str);
  
  free (str);
  [/code]
  The above will convert the array of ints into a single string.
  
  [hr][size=1][leftbr].:EvolutionEngine[rightbr][leftbr].:MicroOS Operating System[rightbr][leftbr][link=http://www.mt2002.sitesled.com]Website[rightbr][/link][/size]
• Lundin

  June 2007

  Noo... very unefficient! And MAX_INT?? Correct me if I'm wrong, but I believe that in the best case, that's defined to 32767. There is no need to allocate 32kb (16-bit system) or 2.1Mb (32-bit system). Plus, MAX_INT isn't ANSI C, INT_MAX is.
  
  A more efficient solution:
  
  [code]#include
  #include
  #include
  
  #if INT_MAX == 32767
  
  #define INT_DIGITS 5
  
  #elif INT_MAX == 2147483647
  
  #define INT_DIGITS 10
  
  #endif
  
  
  
  int main()
  {
  int pNum[] =
  {
  1,
  23,
  45,
  67,
  890,
  };
  int pNum_n = sizeof(pNum) / sizeof(int);
  
  char* str = malloc(sizeof(char) * pNum_n * INT_DIGITS + 1);
  char* str_ptr = str;
  int i;
  
  
  for(i=0; i<pNum_n; i++)
  {
  sprintf(str_ptr, "%d", pNum[i]);
  str_ptr += strlen(str_ptr);
  }
  
  printf ("%s", str);
  getchar();
  
  free (str);
  return 0;
  }[/code]
• mathy

  June 2007

  Thank you very much for your helps!! It's working good now