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~~~

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.

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.