在C中读写多行数据文件

Question

I'm having trouble reading and writing more than one line of data from a file. The problem is to read multiple lines of binary from a file and convert it to decimal and write the multiple lines of decimal to a new file. I had no problem getting the program to convert one line of binary to decimal the trouble comes when I have multiple lines. Here is my code so far:

#include <stdio.h>
#include <string.h>
#define NULL 0

int main() {
  FILE *ptdata, *ptresult;
  char bin[32];
  int i, r = 0, len;
  ptdata = fopen("data.txt", "r");
  ptresult = fopen("result.txt", "w");
  if (ptdata == NULL) printf("Error cannot open file");
  else {
    while (fgets(bin, 32, ptdata) != NULL);
    len = strlen(bin);
    for (i = 0; i < len; i++) {
      r = r * 2 + (bin[i] == '1' ? 1 : 0);
    }
    printf("%d\n", r);
    fprintf(ptresult, "%d\n", r);
    fclose(ptdata);
    fclose(ptresult);
  }
  return 0;
}

Answer 1

Here is the error:

while(fgets(bin,32,ptdata)!=NULL); 
                               //^^^You have semicolon 
                              //here which ends the while loop

You should do the following:

 while(fgets(bin,32,ptdata)!=NULL){
    len = strlen(bin);
    r = 0 ;
    for(i = 0; i < len; i++)
    {
       r = r * 2 + (bin[i] == '1' ? 1 : 0);
    }

    printf("%d\n",r);
    fprintf(ptresult,"%d\n",r);
}

Answer 2

Your while loop has been prematurely terminated

while(fgets(bin,32,ptdata)!=NULL);
                                ^^^