Question

what happens is it gets all the input from fp1 first and then gets input from fp2. Why is it that way? Can’t you get input from 2 different file pointers at the same time inside a while statement?

/*checks if 2 text files are identical */
#include <stdio.h>
int main(void)
{
    FILE *fp1,*fp2;
    char buf1,buf2;
    int flag = 1;
    fp1 = fopen("textfile1.txt","r");
    fp2 = fopen("textfile2.txt","r");
    /* putting them inside a while statement causes a logical error? why */
    while(fscanf(fp1,"%c",&buf1) == 1 ||fscanf(fp2,"%c",&buf2) == 1)
    {
        printf("buf1: %c, buf2: %c\n",buf1,buf2);
        if(buf1 != buf2)
        {
            flag = 0;
            //break;
        }
    }
    if(flag == 1)
        printf("SAME");
    else
        printf("NOT SAME");
    fclose(fp1);
    fclose(fp2);
    return 0;
}

Answer 1

Your while statement is short circuiting. When using the OR (||) operator, if the first expression is true, the second doesn’t not get executed.

I’m not entirely sure what you’re trying to achieve with the OR (||) operator, maybe you actually need an AND (&&)?