/*
 * Copyright (c) 1980, 1987, 1992, 1993
 *      The 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.
 *
 * @(#)head.c   8.2 (Berkeley) 5/4/95
 * $FreeBSD: src/usr.bin/head/head.c,v 1.10.2.1 2002/02/16 12:29:04 dwmalone Exp $
 */

#include <ctype.h>
#include <err.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

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

static void     head(FILE *, size_t);
static void     head_bytes(FILE *, size_t);
static void     obsolete(char *[]);
static void     usage(void) __dead2;

int
main(int argc, char **argv)
{
        int ch;
        FILE *fp;
        bool first;
        bool qflag = false, vflag = false;
        int linecnt = -1, bytecnt = -1, eval = 0;
        char *ep;

        obsolete(argv);
        while ((ch = getopt(argc, argv, "c:n:qv")) != -1) {
                switch(ch) {
                case 'c':
                        bytecnt = strtol(optarg, &ep, 10);
                        if (*ep != 0 || bytecnt <= 0)
                                errx(1, "illegal byte count -- %s", optarg);
                        break;
                case 'n':
                        linecnt = strtol(optarg, &ep, 10);
                        if (*ep != 0 || linecnt <= 0)
                                errx(1, "illegal line count -- %s", optarg);
                        break;
                case 'q':
                        qflag = true;
                        vflag = false;
                        break;
                case 'v':
                        vflag = true;
                        qflag = false;
                        break;
                default:
                        usage();
                }
        }
        argc -= optind;
        argv += optind;

        if (linecnt != -1 && bytecnt != -1)
                errx(1, "can't combine line and byte counts");
        if (linecnt == -1 )
                linecnt = 10;
        if (*argv) {
                first = true;
                for (; *argv; ++argv) {
                        if ((fp = fopen(*argv, "r")) == NULL) {
                                warn("%s", *argv);
                                eval = 1;
                                continue;
                        }
                        if (vflag || (!qflag && argc > 1)) {
                                printf("%s==> %s <==\n",
                                    first ? "" : "\n", *argv);
                                first = false;
                        }
                        if (bytecnt == -1)
                                head(fp, linecnt);
                        else
                                head_bytes(fp, bytecnt);
                        fclose(fp);
                }
        } else if (bytecnt == -1)
                head(stdin, linecnt);
        else
                head_bytes(stdin, bytecnt);

        exit(eval);
}

static void
head(FILE *fp, size_t cnt)
{
        char *cp;
        size_t error, readlen;

        while (cnt && (cp = fgetln(fp, &readlen)) != NULL) {
                error = fwrite(cp, sizeof(char), readlen, stdout);
                if (error != readlen)
                        err(1, "stdout");
                cnt--;
        }
}

static void
head_bytes(FILE *fp, size_t cnt)
{
        char buf[4096];
        size_t readlen;

        while (cnt) {
                if (cnt < sizeof(buf))
                        readlen = cnt;
                else
                        readlen = sizeof(buf);
                readlen = fread(buf, sizeof(char), readlen, fp);
                if (readlen == 0)
                        break;
                if (fwrite(buf, sizeof(char), readlen, stdout) != readlen)
                        err(1, "stdout");
                cnt -= readlen;
        }
}

static void
obsolete(char **argv)
{
        char *ap;

        while ((ap = *++argv)) {
                /* Return if "--" or not "-[0-9]*". */
                if (ap[0] != '-' || ap[1] == '-' || !isdigit(ap[1]))
                        return;
                if ((ap = malloc(strlen(*argv) + 2)) == NULL)
                        err(1, "malloc failed");
                ap[0] = '-';
                ap[1] = 'n';
                strcpy(ap + 2, *argv + 1);
                *argv = ap;
        }
}

static void __dead2
usage(void)
{
        fprintf(stderr,
                "usage: head [-q | -v] [-n lines | -c bytes] [file ...]\n");
        exit(1);
}