func.c

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/**
 * In-class work from 2/2.
 *
 * Passing by value, with pointers, and showing how status codes / perror work.
 */

#include <stdio.h>
#include <fcntl.h>

/* Admittedly, this cool thing is not that cool. */
int cool_thing(long int *a)
{
    if (*a > 1000000) {
        return -1;
    }

    /* I dub this starfest 2021. Look at all those *s */
    *a = *a * *a;

    int ret = cool_thing(a);
    if (ret == -1) {
        return -1;
    }

    return 0;
}

void set_three(long int *a)
{
    /* Figure out what's at the memory location in a, set its value to 3 */
    *a = 3;
}

void swap(long int *a, long int *b)
{
    printf("a is: %p\n", a);
    printf("b is: %p\n", b);

    long temp = *a;
    *a = *b;
    *b = temp;
}

int main(void)
{
    printf("The size of a pointer is: %zu\n", sizeof(int *));

    long int a = 12;
    long int b = 4;

    printf("Addresses of a, b: %p, %p\n", &a, &b);
    printf("a: %ld, b: %ld\n", a, b);

    swap(&a, &b);

    printf("a: %ld, b: %ld\n", a, b);

    set_three(&a);

    printf("a: %ld, b: %ld\n", a, b);

    int ret = cool_thing(&b);
    printf("a: %ld, b: %ld, and the return value is: %i\n", a, b, ret);

    int fd = open("blah.c", O_RDONLY);
    if (fd == -1) {
        perror("open");
        /* non zero exit code to indicate program failure */
        return 1;
    }

    printf("The file descriptor is: %d\n", fd);

    return 0;
}