a question about file output

here is my code:

Code:

---

#include<stdlib.h>
#include<stdio.h>

#define MaxString 10

void
Read(FILE *fpin,char *s)  /* read characters in input file */
{
        char c;
        c=fgetc(fpin);

        while(c!=' '&&c!='\n')
        {
            *(s++)=c;
            c=fgetc(fpin);
        }
        *s='\0';
}

float
TypeChange(char*s)  /* change a string into a float number */
{
        int i=0,j=0;
        float m=0;

        while(s[i]!='\0')
        {
            if(s[i]=='.')
            j=0;
            else
            {
                m=10*m+s[i]-'0';
                j++;
              }
              i++;
        }
        if(i==j)
                return m;
        else
        {
                for(;j!=0;j--);
                m=m/10;
                return m;
        }
}

int
main()
{
        char s[MaxString];
        float array[100];
        int i=0;
        FILE *fpin,*fpout;
        fpin=fopen("input.txt","r");
        fpout=fopen("output.txt","w");

        while(!feof(fpin))      /* some confusion here */
        {
                Read(fpin,s);
                array[i]=TypeChange(s);
                fprintf(fpout,"%f",array[i]);
                i++;
        }

        fclose(fpin);
        fclose(fpout);
        return 0;
}

---

i am a little confused about feof() function,i just want to read from
the input.txt file and output the numbers of input file into output.txt file,but when i excute the program,i could see nothing
in the output file.

the input file is like this:
0 1 3.3[return]

Could anyone help me?thx~~~

Quote:

---

Originally Posted by wang8442

here is my code:
<...>
i am a little confused about feof() function,i just want to read from
the input.txt file and output the numbers of input file into output.txt file,but when i excute the program,i could see nothing
in the output file.

the input file is like this:
0 1 3.3[return]

---

Here is your code commented (-ed-). Please, read the comment carefully and ask for details if needed :

Code:

---

/* -ed-
 * Code reindented
 * Comments moved (To prevent from having lines longer than 76 columns)
 * Code full-braced.
 * Useless macro removed
 */

#include<stdlib.h>
#include<stdio.h>

/* read characters in input file */
void Read (FILE * fpin, char *s)
{
  char c;
  c = fgetc (fpin);

  while (c != ' ' && c != '\n')
  {
      *(s++) = c;
      c = fgetc (fpin);
  }
  *s = '\0';
}

/* change a string into a float number */
float TypeChange (char *s)
{
  int i = 0, j = 0;
  float m = 0;

  while (s[i] != '\0')
  {
      if (s[i] == '.')
      {
        j = 0;
      }
      else
      {
        m = 10 * m + s[i] - '0';
        j++;
      }
      i++;
  }
  if (i == j)
  {
      return m;
  }
  else
  {
      for (; j != 0; j--);
      m = m / 10;
      return m;
  }
}

int main ()
{
  char s[10];
  float array[100];
  int i = 0;
  FILE *fpin, *fpout;
  fpin = fopen ("input.txt", "r");
/* -ed-
 * fopen() can fail returning NULL.
 * This should have been tested before use.
 * (typically, I have no 'input.txt' file on my machine).
 */ 
  fpout = fopen ("output.txt", "w");

  while (!feof (fpin))        /* some confusion here */
/* -ed-
 * The main confusion is about the feof() function itself.
 * Calling this functions only makes sense once you have detected an
 * 'end of reading' condition. Each time a stream reading function is
 * called, and end of reading can happen, mainly for two reasons :
 * - An error occured
 * - The end of file was reached.
 * This is why the readind function returns some information (NULL, EOF)
 * to indicate this condition. This should be tested, and now,
 * and only now, the feof() and ferror() functions can be called to
 * identify the exact cause of the end of reading, if you really want to
 * know about these details.
 */
 
  {
      Read (fpin, s);
/* -ed-
 * Typically, this function should return some 'end of reading' status...
 *
 * Note that the interface of this function is dangerous.
 * If I got it well, 's' the address of an output array of char.
 * You forgot to pass the sizeof of it, making the Read() function
 * unsafe (rejected by my Quality Control Service)
 */     
      array[i] = TypeChange (s);
      fprintf (fpout, "%f", array[i]);
      i++;
  }

  fclose (fpin);
  fclose (fpout);
  return 0;
}

---

And here is your code fixed and simplified:

Code:

---

#include<stdlib.h>
#include<stdio.h>

/* read characters in input file */
int Read (FILE * fpin, char *s, size_t size)
{
  size_t i = 0;
  int c;

  while ((c = fgetc (fpin)) != ' '
          && c != '\n'
          && c != EOF
          && i < size - 1)
  {
      s[i] = c;
      i++;
  }
  s[i] = '\0';

  return c;
}

/* change a string into a float number */
float TypeChange (char *s)
{
  int i = 0, j = 0;
  float m = 0;

  while (s[i] != '\0')
  {
      if (s[i] == '.')
      {
        j = 0;
      }
      else
      {
        m = 10 * m + s[i] - '0';
        j++;
      }
      i++;
  }
  if (i == j)
  {
      return m;
  }
  else
  {
      for (; j != 0; j--);
      m = m / 10;
      return m;
  }
}

int main (void)
{
#define F_IN "input.txt"
#define F_OUT "output.txt"

  FILE *fpin = fopen (F_IN, "r");

  if (fpin != NULL)
  {
      FILE *fpout = fopen (F_OUT, "w");

      if (fpout != NULL)
      {
        char s[10];

        while (Read (fpin, s, sizeof s) != EOF)
        {
            float value = TypeChange (s);
            fprintf (fpout, "%f\n", value);
        }

        fclose (fpout);
      }
      else
      {
        perror (F_OUT);
      }
      fclose (fpin);
  }
  else
  {
      perror (F_IN);
  }
  return 0;
}

---

Note that the whole thing could have been done with fgets() and strtod() in an tenth of lines...

Doesn't the use of array[100] also fail your Quality Control Service? Especially since the use of an array there seems superfluous - you're only dealing with one float at a time, so just use a single float.

Quote:

---

Originally Posted by DonFiasco

Doesn't the use of array[100] also fail your Quality Control Service? Especially since the use of an array there seems superfluous - you're only dealing with one float at a time, so just use a single float.

---

This has been seen later. See my amended post.