/*      $OpenBSD: head.c,v 1.24 2022/02/07 17:19:57 cheloha Exp $       */

/*
 * Copyright (c) 1980, 1987 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <limits.h>
#include <err.h>
#include <errno.h>
#include <unistd.h>

int head_file(const char *, long, int);
static void usage(void);

/*
 * head - give the first few lines of a stream or of each of a set of files
 *
 * Bill Joy UCB August 24, 1977
 */

int
main(int argc, char *argv[])
{
        const char *errstr;
        int     ch;
        long    linecnt = 10;
        int     status = 0;

        if (pledge("stdio rpath", NULL) == -1)
                err(1, "pledge");

        /* handle obsolete -number syntax */
        if (argc > 1 && argv[1][0] == '-' &&
            isdigit((unsigned char)argv[1][1])) {
                linecnt = strtonum(argv[1] + 1, 1, LONG_MAX, &errstr);
                if (errstr != NULL)
                        errx(1, "count is %s: %s", errstr, argv[1] + 1);
                argc--;
                argv++;
        }

        while ((ch = getopt(argc, argv, "n:")) != -1) {
                switch (ch) {
                case 'n':
                        linecnt = strtonum(optarg, 1, LONG_MAX, &errstr);
                        if (errstr != NULL)
                                errx(1, "count is %s: %s", errstr, optarg);
                        break;
                default:
                        usage();
                }
        }
        argc -= optind, argv += optind;

        if (argc == 0) {
                if (pledge("stdio", NULL) == -1)
                        err(1, "pledge");

                status = head_file(NULL, linecnt, 0);
        } else {
                for (; *argv != NULL; argv++)
                        status |= head_file(*argv, linecnt, argc > 1);
        }

        return status;
}

int
head_file(const char *path, long count, int need_header)
{
        const char *name;
        FILE *fp;
        int ch, status = 0;
        static int first = 1;

        if (path != NULL) {
                name = path;
                fp = fopen(name, "r");
                if (fp == NULL) {
                        warn("%s", name);
                        return 1;
                }
                if (need_header) {
                        printf("%s==> %s <==\n", first ? "" : "\n", name);
                        if (ferror(stdout))
                                err(1, "stdout");
                        first = 0;
                }
        } else {
                name = "stdin";
                fp = stdin;
        }

        while ((ch = getc(fp)) != EOF) {
                if (putchar(ch) == EOF)
                        err(1, "stdout");
                if (ch == '\n' && --count == 0)
                        break;
        }
        if (ferror(fp)) {
                warn("%s", name);
                status = 1;
        }

        fclose(fp);

        return status;
}


static void
usage(void)
{
        fputs("usage: head [-count | -n count] [file ...]\n", stderr);
        exit(1);
}