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

void _write_file(char const* filename, char const* text) {
    FILE* file = fopen(filename, "w");
    fputs(text, file);
    fclose(file);
}


int main(int argc, char* argv[]) {
    // want the file to exist, so we get a error
    // unique to this example
    _write_file("some_text.txt", "abcd");   
    // this should be in write mode, not read mode
    FILE* file = fopen("some_text.txt", "r");

    // my data abcd is just gone now
    fputc('A', file);
    printf("System error: %d:\n%s\n",
            errno, strerror(errno));
    printf("File error: %d:\n%s\n", 
            ferror(file), strerror(ferror(file)));

    fclose(file);
    return EXIT_SUCCESS;
}
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