issue fgetc() c using while loop

Question

I got a big problem using fgetc() and i can't figure it out... I try to parse a text file, everything compile but at the execution I got an infinite loop or a segfault (Code::blocks), my text file is like that: {"USD_EUR": "0.8631364", "EUR_USD": "1.3964719"} with 16 rates change. I try to put all my float in rate[16]...

FILE* file = NULL;
file = fopen(myFile, "r+");
int value,i;
float rate[16];
char* str = "";
if (file != NULL)
{
    do
    {
        value = fgetc(file);
        printf("%c \n",value);
        while(value > 48 && value < 57)
        {
            value = fgetc(file);
            strcat(str, value);
            //printf("%s \n", str);
        }
        rate[i] = atof(str);
        i++;
        str = "";
    }while(value != 125); // 125 = }

Answer 1

while(value =! EOF); should be while(value != EOF);

It's a big difference. First case is an assignment to the variable value, second case looks if value is not equal to EOF.

EOF is a macro and usually have the value -1, that means that !EOF becomes 0. Since you have a do{} while() it will run once but not more since condition is false.

Answer 2

in the while loop you are assigning the value to the variable value.

     `while(value =! EOF);`

The value of EOF is -1.(i.e) End of file. if it is !-1, then it will take as 0. As it is a do while only once the loop will be executed, next time the condition will be false. So it gets only one character. You can use

`while(value != EOF);`

which means not equal to EOF. Then the condition will be true and the loop will be executed till the condition becomes false.

Answer 3

Declaration of value is incorrect and make that correct.

int value;

While ( value != EOF ) is comparing the value to EOF. Here EOF is a macro having the value as -1. Comparing the value with that. You can see that using cc -E while compiling.

(value =!EOF) means that value =! (-1) So !(-1) comes zero. That will assign to the variable value. So in condition zero is false. So it come out from the loop. And you can check the value of variable value by printing that variable.

Answer 4

The following code does the job of reading/echoing a input file
char by char.

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

char *theFile = "input.txt";

int main()
{
    FILE* file = NULL;
    int value;

    if( NULL == ( file = fopen(theFile, "r") ) )
    { // then fopen failed
        perror( "fopen failed" );
        exit(EXIT_FAILURE );
    }

    // implied else, fopen successful

    while( EOF != (value = fgetc(file) ) )
    {
        printf("%c \n",value);
    } // end while

    return(0);
} // end function: main

Answer 5

while(value =! EOF) is not same as while(value != EOF)

What you need is the latter while(value != EOF)