1/*
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1980, 1987, 1992, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 *    may be used to endorse or promote products derived from this software
17 *    without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32#ifndef lint
33static const char copyright[] =
34"@(#) Copyright (c) 1980, 1987, 1992, 1993\n\
35	The Regents of the University of California.  All rights reserved.\n";
36#endif /* not lint */
37
38#ifndef lint
39#if 0
40static char sccsid[] = "@(#)head.c	8.2 (Berkeley) 5/4/95";
41#endif
42#endif /* not lint */
43#include <sys/cdefs.h>
44__FBSDID("$FreeBSD$");
45
46#include <sys/types.h>
47
48#include <ctype.h>
49#include <err.h>
50#include <getopt.h>
51#include <inttypes.h>
52#include <stdio.h>
53#include <stdlib.h>
54#include <string.h>
55#include <unistd.h>
56
57/*
58 * head - give the first few lines of a stream or of each of a set of files
59 *
60 * Bill Joy UCB August 24, 1977
61 */
62
63static void head(FILE *, int);
64static void head_bytes(FILE *, off_t);
65static void obsolete(char *[]);
66static void usage(void);
67
68static const struct option long_opts[] =
69{
70	{"bytes",	required_argument,	NULL, 'c'},
71	{"lines",	required_argument,	NULL, 'n'},
72	{NULL,		no_argument,		NULL, 0}
73};
74
75int
76main(int argc, char *argv[])
77{
78	int ch;
79	FILE *fp;
80	int first, linecnt = -1, eval = 0;
81	off_t bytecnt = -1;
82	char *ep;
83
84	obsolete(argv);
85	while ((ch = getopt_long(argc, argv, "+n:c:", long_opts, NULL)) != -1)
86		switch(ch) {
87		case 'c':
88			bytecnt = strtoimax(optarg, &ep, 10);
89			if (*ep || bytecnt <= 0)
90				errx(1, "illegal byte count -- %s", optarg);
91			break;
92		case 'n':
93			linecnt = strtol(optarg, &ep, 10);
94			if (*ep || linecnt <= 0)
95				errx(1, "illegal line count -- %s", optarg);
96			break;
97		case '?':
98		default:
99			usage();
100		}
101	argc -= optind;
102	argv += optind;
103
104	if (linecnt != -1 && bytecnt != -1)
105		errx(1, "can't combine line and byte counts");
106	if (linecnt == -1 )
107		linecnt = 10;
108	if (*argv) {
109		for (first = 1; *argv; ++argv) {
110			if ((fp = fopen(*argv, "r")) == NULL) {
111				warn("%s", *argv);
112				eval = 1;
113				continue;
114			}
115			if (argc > 1) {
116				(void)printf("%s==> %s <==\n",
117				    first ? "" : "\n", *argv);
118				first = 0;
119			}
120			if (bytecnt == -1)
121				head(fp, linecnt);
122			else
123				head_bytes(fp, bytecnt);
124			(void)fclose(fp);
125		}
126	} else if (bytecnt == -1)
127		head(stdin, linecnt);
128	else
129		head_bytes(stdin, bytecnt);
130
131	exit(eval);
132}
133
134static void
135head(FILE *fp, int cnt)
136{
137	char *cp;
138	size_t error, readlen;
139
140	while (cnt && (cp = fgetln(fp, &readlen)) != NULL) {
141		error = fwrite(cp, sizeof(char), readlen, stdout);
142		if (error != readlen)
143			err(1, "stdout");
144		cnt--;
145	}
146}
147
148static void
149head_bytes(FILE *fp, off_t cnt)
150{
151	char buf[4096];
152	size_t readlen;
153
154	while (cnt) {
155		if ((uintmax_t)cnt < sizeof(buf))
156			readlen = cnt;
157		else
158			readlen = sizeof(buf);
159		readlen = fread(buf, sizeof(char), readlen, fp);
160		if (readlen == 0)
161			break;
162		if (fwrite(buf, sizeof(char), readlen, stdout) != readlen)
163			err(1, "stdout");
164		cnt -= readlen;
165	}
166}
167
168static void
169obsolete(char *argv[])
170{
171	char *ap;
172
173	while ((ap = *++argv)) {
174		/* Return if "--" or not "-[0-9]*". */
175		if (ap[0] != '-' || ap[1] == '-' || !isdigit(ap[1]))
176			return;
177		if ((ap = malloc(strlen(*argv) + 2)) == NULL)
178			err(1, NULL);
179		ap[0] = '-';
180		ap[1] = 'n';
181		(void)strcpy(ap + 2, *argv + 1);
182		*argv = ap;
183	}
184}
185
186static void
187usage(void)
188{
189
190	(void)fprintf(stderr, "usage: head [-n lines | -c bytes] [file ...]\n");
191	exit(1);
192}
193