How can I make my program more flexible?

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <time.h>

int is_end(char* input) {
	return *input == 0;
}

int is_linebreak(char* input) {
	return *input == '\r' || *input == '\n' || *input == ' ';
}

char* eat_linebreaks(char* input) {
	while (is_linebreak(input))
		++input;

	return input;
}

size_t count_lines(char* input) {
	char* p = input;
	size_t rows = 1;

	if (is_end(p))
		return 0;
	
	while (!is_end(p)) {
		if (is_linebreak(p)) {
			++rows;
			p = eat_linebreaks(p);
		}
		else {
			++p;
		}
	}
	return rows;
}

/* split string by lines */
char** get_lines(char* input, size_t line_count) {
	char* p = input;
	char* from = input;
	size_t length = 0;
	size_t line = 0;
        int i;
	char** lines = (char**)malloc(line_count * sizeof(char*));

	do {
		if (is_end(p) || is_linebreak(p)) {
			lines[line] = (char*)malloc(length + 1);
			for (i = 0; i < length; ++i)
				lines[line][i] = *(from + i);

			lines[line][length] = 0;
			length = 0;
			++line;
			p = eat_linebreaks(p);
			from = p;
			
		}
		else {
			++length;
			++p;
		}
	} while (!is_end(p));

	// Copy the last line as well in case the input doesn't end in line-break
	lines[line] = (char*)malloc(length + 1);
	for (i = 0; i < length; ++i)
		lines[line][i] = *(from + i);

	lines[line][length] = 0;
	++line;


	return lines;
}

int main(int argc, char* argv[]) {
	clock_t start;
	unsigned long microseconds;
	float seconds;
	char** lines;
	size_t size;
	size_t number_of_rows;
	int count;
	int* my_array;
	start = clock();

	FILE *stream;
	char *contents;
	int fileSize = 0;
        int i;

	// Open file, find the size of it
	stream = fopen(argv[1], "rb");
	fseek(stream, 0L, SEEK_END);
	fileSize = ftell(stream);
	fseek(stream, 0L, SEEK_SET);

	// Allocate space for the entire file content
	contents = (char*)malloc(fileSize + 1);

	// Stream file into memory
	size = fread(contents, 1, fileSize, stream);
	contents[size] = 0; 
	fclose(stream);

	// Count rows in content
	number_of_rows = count_lines(contents);

	// Get array of char*, one for each line
	lines = get_lines(contents, number_of_rows);
	
	// Get the numbers out of the lines
	count = atoi(lines[0]); // First row has count
	my_array = (int*)malloc(count * sizeof(int));
	for (i = 0; i < count; ++i) {
		my_array[i] = atoi(lines[i + 1]);
	}

	microseconds = clock() - start;
	seconds = microseconds / 1000000.0f;
	printf("Took %fs", seconds);


	return 0;
}