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

int main(int argc, char* argv[]) {
    // Create a text file containing "Yo!" plus a null terminator (weird thing to do).
    FILE* fp = fopen("l.txt", "w");
    fprintf(fp, "Yo!");
    fputc('\0', fp);  // This is WEIRD.  Normally:  Do not write '\0' to a text file.
    fclose(fp); // RULE:  If you open a file, you must close it (once).

    // Read an int from the file.  This only works because the file contains 4 bytes.
    fp = fopen("l.txt", "r");   // mode "r" means we want to read a file.  "a" means append to the end
    int num_from_file;  // will be initialized by fread(…).
    int* a_num_from_file = &num_from_file;
    fread(&num_from_file, sizeof(*a_num_from_file), 1, fp);
    fclose(fp); // RULE:  If you open a file, you must close it (once).

    printf("num_from_file == 0x%08x   #  %d\n", num_from_file, num_from_file);

    return EXIT_SUCCESS;
}
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