head.c revision 330897 
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 * 4. 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: stable/11/usr.bin/head/head.c 330897 2018-03-14 03:19:51Z eadler $");
45
46#include <sys/types.h>
47
48#include <ctype.h>
49#include <err.h>
50#include <inttypes.h>
51#include <stdio.h>
52#include <stdlib.h>
53#include <string.h>
54#include <unistd.h>
55
56/*
57 * head - give the first few lines of a stream or of each of a set of files
58 *
59 * Bill Joy UCB August 24, 1977
60 */
61
62static void head(FILE *, int);
63static void head_bytes(FILE *, off_t);
64static void obsolete(char *[]);
65static void usage(void);
66
67int
68main(int argc, char *argv[])
69{
70	int ch;
71	FILE *fp;
72	int first, linecnt = -1, eval = 0;
73	off_t bytecnt = -1;
74	char *ep;
75
76	obsolete(argv);
77	while ((ch = getopt(argc, argv, "n:c:")) != -1)
78		switch(ch) {
79		case 'c':
80			bytecnt = strtoimax(optarg, &ep, 10);
81			if (*ep || bytecnt <= 0)
82				errx(1, "illegal byte count -- %s", optarg);
83			break;
84		case 'n':
85			linecnt = strtol(optarg, &ep, 10);
86			if (*ep || linecnt <= 0)
87				errx(1, "illegal line count -- %s", optarg);
88			break;
89		case '?':
90		default:
91			usage();
92		}
93	argc -= optind;
94	argv += optind;
95
96	if (linecnt != -1 && bytecnt != -1)
97		errx(1, "can't combine line and byte counts");
98	if (linecnt == -1 )
99		linecnt = 10;
100	if (*argv) {
101		for (first = 1; *argv; ++argv) {
102			if ((fp = fopen(*argv, "r")) == NULL) {
103				warn("%s", *argv);
104				eval = 1;
105				continue;
106			}
107			if (argc > 1) {
108				(void)printf("%s==> %s <==\n",
109				    first ? "" : "\n", *argv);
110				first = 0;
111			}
112			if (bytecnt == -1)
113				head(fp, linecnt);
114			else
115				head_bytes(fp, bytecnt);
116			(void)fclose(fp);
117		}
118	} else if (bytecnt == -1)
119		head(stdin, linecnt);
120	else
121		head_bytes(stdin, bytecnt);
122
123	exit(eval);
124}
125
126static void
127head(FILE *fp, int cnt)
128{
129	char *cp;
130	size_t error, readlen;
131
132	while (cnt && (cp = fgetln(fp, &readlen)) != NULL) {
133		error = fwrite(cp, sizeof(char), readlen, stdout);
134		if (error != readlen)
135			err(1, "stdout");
136		cnt--;
137	}
138}
139
140static void
141head_bytes(FILE *fp, off_t cnt)
142{
143	char buf[4096];
144	size_t readlen;
145
146	while (cnt) {
147		if ((uintmax_t)cnt < sizeof(buf))
148			readlen = cnt;
149		else
150			readlen = sizeof(buf);
151		readlen = fread(buf, sizeof(char), readlen, fp);
152		if (readlen == 0)
153			break;
154		if (fwrite(buf, sizeof(char), readlen, stdout) != readlen)
155			err(1, "stdout");
156		cnt -= readlen;
157	}
158}
159
160static void
161obsolete(char *argv[])
162{
163	char *ap;
164
165	while ((ap = *++argv)) {
166		/* Return if "--" or not "-[0-9]*". */
167		if (ap[0] != '-' || ap[1] == '-' || !isdigit(ap[1]))
168			return;
169		if ((ap = malloc(strlen(*argv) + 2)) == NULL)
170			err(1, NULL);
171		ap[0] = '-';
172		ap[1] = 'n';
173		(void)strcpy(ap + 2, *argv + 1);
174		*argv = ap;
175	}
176}
177
178static void
179usage(void)
180{
181
182	(void)fprintf(stderr, "usage: head [-n lines | -c bytes] [file ...]\n");
183	exit(1);
184}
185