I am writing a function to do "while" , but why error?

Question

I am writing a function to do "while" to count the numbers of alphabetic and digits in a text file. I would like to seperate it to 2 functions of 2 "while". But it error after I create the first function. What's wrong of it?

    #include "stdafx.h"
    #include "stdlib.h"
    #include "ctype.h"

    void countDig (FILE* input, char num, int numCount);

    int _tmain(void)

    {



     FILE* input; 
       char num; 
       char ch;
       int numCount = 0; 
       int chCount = 0;


   input = fopen("123.txt", "r"); 

   if (!input) 
  { 
    printf("No file \a\n"); 
    exit (101); 
  } 



     while ((fscanf(input, " %c", &ch)) == 1)
    { 
      printf(" %c\n", ch); 
      if (isalpha(ch)) 
       chCount++; 

    } 

     countDig (input, num, numCount);







  printf("ch count: %d", chCount); 




    return 0;
}


void countDig (FILE* input, char num, int numCount)
{
    FILE* f;
    char n;
    int nc;


   while ((fscanf(f, " %c", &n)) == 1)
    { 
      printf(" %c\n", n); 
      if (isdigit(n)) 
       nc++; 
    } 
     printf("number count: %d", nc); 

   return;

}

---

after correction:

#include "stdafx.h"
#include "stdlib.h"
#include "ctype.h"

void countDig (FILE* input, char num, int numCount);

int _tmain(void)
{
  FILE* input; 
   char num; 
   char ch;
   int numCount = 0; 
   int chCount = 0;

   input = fopen("123.txt", "r"); 

   if (!input) 
  { 
    printf("No file \a\n"); 
    exit (101); 
  } 


     while ((fscanf(input, " %c", &ch)) == 1)
    { 
      printf(" %c\n", ch); 
      if (isalpha(ch)) 
       chCount++; 

    } 

     countDig (input, num, numCount);



  printf("ch count: %d", chCount); 

    return 0;
}


void countDig (FILE* input, char num, int numCount)
{
    char n;
    int nc = 0;


   while ((fscanf(input, " %c", &n)) == 1)
    { 
      printf(" %c\n", n); 
      if (isdigit(n)) 
       nc++; 
    } 
     printf("number count: %d", nc); 

   return;

}

Answer 1

Your countDig function takes a FILE* but doesn't use it. Instead it uses an unintialised local FILE*:

void countDig (FILE* input, char num, int numCount)
{
    FILE* f;
    char n;
    int nc;
    while ((fscanf(f, " %c", &n)) == 1)   // f is uninitialised here

You probably meant something like this:

void countDig (FILE* input, char num, int numCount)
{
    char n;
    int nc;
    while ((fscanf(input, " %c", &n)) == 1)

You're also using nc without initialising it - C doesn't automatically set variables to zero; you have to do that yourself:

int nc = 0;

Edit after followup code: As far as I can see you have a couple of other uninitialised variables, but apart from that the code should work. The only other issue is that countDig() may not find anything because the initial loop in _tmain() has read all the way to the end of the file. countDig() will continue to read where the main loop finished, which could be the end of the file.

Answer 2

In your countDig function, your File* f; variable is not initialized, neither is nc that you're incrementing.

Finally in this funciton, what was the intent of the numCount parameter?

Answer 3

Counting letters you get to the end of the file and then trying to read some more from an uninitialised file handle...

Answer 4

You need to close and re-open the FILE*. After the first while loop the FILE* is at the end of the file, so when you try to loop through it again in the function it wont work.