#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <fcntl.h>

#include <sys/mman.h>

int main(int argc, char const *argv[])

{

char name[] = "file.txt";

int strLength = 0, num, i = 0, position = 0, k = 0;

int file1;

file1 = open(name, O_RDONLY);

int len = lseek(file1, 0, SEEK_END);

void *src;

char *findPtr;

if((src = mmap(0, len, PROT_READ, MAP_SHARED, file1, 0)) == MAP_FAILED){

perror("mmap error");

}

int *lengths = NULL;

int *positions = NULL;

lengths = (int*)malloc(1 * sizeof(int));

findPtr = src;

while(findPtr[k] != 0){

if (findPtr[k] == '\n')

{

lengths[i] = strLength;

i++;

position = k + 1;

positions = (int*)realloc(positions, (i+1) * sizeof(int));

lengths = (int*)realloc(lengths, (i+1) * sizeof(int));

positions[i] = position;

strLength = 0;

}else{

strLength++;

}

k++;

}

lengths[i] = strLength;

positions = (int*)realloc(positions, (i + 2) * sizeof(int));

positions[i+1] = lseek(findPtr, 0, SEEK_END);

for (int k = 0; k < i; k++)

{

printf("pos %d, len %d\n", positions[k], lengths[k]);

}

do{

printf("\nВведите номер строки\n");

scanf("%d", &num);

if(num > i+1){

printf("В файле всего %d строк(и), введите номер строки из этого диапазона\n", i+1);

}else if(num != 0){

strLength = lengths[num-1];

k = 0;

while(k < strLength){

printf("%c", findPtr[positions[num-1] + k]);

k++;

}

}

} while(num != 0);

return 0;

}