Hey, Nikita

#include<stdio.h>
#include<stdlib.h>
#pragma warning(disable : 4996) //for VS to permit fopen
/*Prints all the strings starting from "hello" from file which name is typed in by user*/

int  getfilename(char *filename, const int maxlen);
void printstrings(char *filename, char *compareto, const int maxlen);
int main(void) {
    const int maxlen = 100;
    char * filename = (char *)calloc(maxlen + 1, sizeof(char));
    char compareto[] = "hello";
    int flag = getfilename(filename, maxlen);
    if (flag == -1) {
        printf("error: filename too long\n");
        return -1;
    }
    printf("Opening file: %s\n", filename);
    printstrings(filename, compareto, maxlen);
    free(filename);
    return 0;
}

int  getfilename(char *filename, const int maxlen) {
    int buf;
    int i = 0;
    printf("enter full path to file\n");
    while ((buf = getc(stdin)) != NULL && buf != '\n' && buf != ' ' && i <= maxlen)
        filename[i++] = buf;
    if (i == maxlen)
        return -1;
    return 0;
}

void printstrings(char *filename, char *compareto, const int maxlen) {
    FILE * fp = fopen(filename, "r"); //c://input.txt
    int *buf  = (char *)calloc(maxlen, sizeof(char));
    int i = 0;
    if (fp == NULL) {
        printf("error opening file\n");
        exit(-1);
    }
    while (buf[0] != '\n' && buf[0] != EOF) {
        int flag = 1;
        for (i = 0; i < maxlen && (buf[i] = getc(fp)) != '\n'; i++) {
            if (feof(fp)) {
                printf("error reading file\n");
                exit(-1);
            }
            buf[i] ;
        }
        i = 0;
        while (compareto[i] != 0) {
            if (compareto[i] != buf[i]) { //if first substring of buf isn't "hello"
                flag = 0;
                break;
            }
            i++;
        }
        if (flag == 1) {
            i = 0;
            while (buf[i] != 0) {
                putc(buf[i], stdout);
                buf[i] = 0;
                i++;
            }
        }
    }
}