C: fgets always NULL

Question

I'm playing with file I/O in C.. I'm trying to use fgets to read data in from one file and output it to another file. The problem is that it always returns NULL and so nothing gets copied to the output file. Here's my code:

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

int main()
{
    FILE *fpIn;
    FILE *fpOut;

    if ((fpIn = fopen("C:\\testIn.txt", "r") == NULL))
    {
        printf("Cannot open input file!\n");
        exit(1);
    }

    if ((fpOut = fopen("C:\\testOut.txt", "a") == NULL))
    {
        printf("Cannot open output file!\n");
        exit(1);
    }

    char buffer[128];
    while (fgets(buffer, 128, fpIn) != NULL)
    {
        fputs(buffer, fpOut);
    }

    fclose(fpIn);
    fclose(fpOut);

    system("PAUSE");
    return 0;
}

another thing; when I tried using "a+f" in the second arg for fopen, it didn't work.

Answer 1

if ((fpOut = fopen("C:\\testOut.txt", "a") == NULL))

Should be

if ((fpOut = fopen("C:\\testOut.txt", "a")) == NULL)

Same on the input file. If you are new to C, I'd suggest do one thing at a time to make it easier to track down issues. eg

fpOut = fopen("C:\\testOut.txt", "a");
if(fpOut == NULL) {
    ...