fases/core/tail.c

/* SPDX-License-Identifier: BSD-3-Clause */
/*
 * Copyright (C) 2022, 2023 Ferass El Hafidi <vitali64pmemail@protonmail.com>
 */
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>

#define REQ_PRINT_USAGE /* Require print_usage() from ../common/common.h */
#define REQ_ERRPRINT /* Require errprint() from ../common/common.h */
#define DESCRIPTION "Copy the last part of files."
#define OPERANDS    "[-n number] [file] ..."
#include "../common/common.h"

int main(int argc, char *const argv[]) {
	int argument, i = 1, lines, file_lines;
	FILE *file;

	char s[4096], *argv0 = strdup(argv[0]);

	while ((argument = getopt(argc, argv, "n:")) != -1) {
		if (argument == '?' || argument == ':') {
			print_usage(argv[0], DESCRIPTION, OPERANDS, VERSION);
			return 1;
		}
		else if (argument == 'n') {
			lines = strtol(optarg, NULL, 10);
			if (errno) return errprint(argv[0], "strtol()", errno);
		}
		else
			lines = 10;
	} argc -= optind; argv += optind;
	if (argc < 1) {
		while (read(STDIN_FILENO, s, 4096) > 0)
			printf("%s", s);
	}
	if (!lines) lines = 10;
	for (i = 0; i != argc; i++) {
		if (strcmp(argv[i], "-")) file = fopen(argv[i], "r");
		else while (read(STDIN_FILENO, s, 4096) > 0) printf("%s", s);
		if (file == NULL)
			return errprint(argv[0], argv[i], errno); /* Something went wrong */
		while (fgets(s, 4096, file) != NULL) 
			file_lines++; /* Get number of lines */
		fclose(file);
		file_lines = file_lines - lines;
		if (strcmp(argv[i], "-")) file = fopen(argv[i], "r");
		while (fgets(s, 4096, file) != NULL) {
			if (errno) return errprint(argv0, argv[i], errno);
			if (file_lines == 0) printf("%s", s);
			else file_lines--;
		}
	}

	return errprint(argv0, NULL, errno);
}