#include <stdio.h>
#include <malloc.h>
#include <string.h>

char *getline2(FILE *f) {
    int sym;
    char *mystring = malloc(1 * sizeof(char));
    int capacity = 1;
    int len = 0;
    if (!f) {
        return NULL;
    }
    while ((sym = fgetc(f))) {
        if (len == capacity - 1) {
            capacity *= 2;
            char* tmp_mystring = mystring;
            mystring = realloc(tmp_mystring,capacity);
            if(!mystring){
                return NULL;
            }
        }
        mystring[len] = sym;
        ++len;
        if(sym == '\n'){
            mystring[len] = '\0';
            return mystring;
        }
    }
    if(strlen(mystring) == 0){
        return NULL;
    }
    mystring[len] = '\0';
    return mystring;
}