#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>

size_t count_char(const char *restrict source, const size_t len, const char cmp, const size_t counter) [[reproducible]] {
    size_t c = counter;
    for (size_t i = 0; i < len; ++i) {
        if (source[i] == cmp) {
            ++c;
        }
    }
    return c;
}

int main(int argc, char **argv) {
    if (argc <= 1) {
        fprintf(stderr, "Error requires at least one filename as argument.\n");
        return EXIT_FAILURE;
    }
    for (int i = 1; i < argc; ++i) {
        FILE *fptr = fopen(argv[i], "rb");
        if (fptr == nullptr) {
            fprintf(stderr, "Error could not open file: %s\n", argv[i]);
            continue;
        }
        static constexpr size_t BUFFER_SIZE = 4096;
        static char buffer[BUFFER_SIZE] = {};
        size_t bytes = 0;
        size_t counter = 0;
        while ((bytes = fread(buffer, sizeof(char), BUFFER_SIZE, fptr)) != 0) {
            counter = count_char(buffer, bytes, '\n', counter);
        }
        printf("%s: %zu\n", argv[i], counter);
        fclose(fptr);
    }
    return EXIT_SUCCESS;
}