head.c revision 99112 
1/*
2 * Copyright (c) 1980, 1987, 1992, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by the University of
16 *	California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#ifndef lint
35static const char copyright[] =
36"@(#) Copyright (c) 1980, 1987, 1992, 1993\n\
37	The Regents of the University of California.  All rights reserved.\n";
38#endif /* not lint */
39
40#ifndef lint
41#if 0
42static char sccsid[] = "@(#)head.c	8.2 (Berkeley) 5/4/95";
43#endif
44#endif /* not lint */
45#include <sys/cdefs.h>
46__FBSDID("$FreeBSD: head/usr.bin/head/head.c 99112 2002-06-30 05:25:07Z obrien $");
47
48#include <sys/cdefs.h>
49__FBSDID("$FreeBSD: head/usr.bin/head/head.c 99112 2002-06-30 05:25:07Z obrien $");
50
51#include <sys/types.h>
52
53#include <ctype.h>
54#include <err.h>
55#include <stdio.h>
56#include <stdlib.h>
57#include <string.h>
58#include <unistd.h>
59
60/*
61 * head - give the first few lines of a stream or of each of a set of files
62 *
63 * Bill Joy UCB August 24, 1977
64 */
65
66static void head(FILE *, int);
67static void head_bytes(FILE *, size_t);
68static void obsolete(char *[]);
69static void usage(void);
70
71int
72main(int argc, char *argv[])
73{
74	int ch;
75	FILE *fp;
76	int first, linecnt = -1, bytecnt = -1, eval = 0;
77	char *ep;
78
79	obsolete(argv);
80	while ((ch = getopt(argc, argv, "n:c:")) != -1)
81		switch(ch) {
82		case 'c':
83			bytecnt = strtol(optarg, &ep, 10);
84			if (*ep || bytecnt <= 0)
85				errx(1, "illegal byte count -- %s", optarg);
86			break;
87		case 'n':
88			linecnt = strtol(optarg, &ep, 10);
89			if (*ep || linecnt <= 0)
90				errx(1, "illegal line count -- %s", optarg);
91			break;
92		case '?':
93		default:
94			usage();
95		}
96	argc -= optind;
97	argv += optind;
98
99	if (linecnt != -1 && bytecnt != -1)
100		errx(1, "can't combine line and byte counts");
101	if (linecnt == -1 )
102		linecnt = 10;
103	if (*argv) {
104		for (first = 1; *argv; ++argv) {
105			if ((fp = fopen(*argv, "r")) == NULL) {
106				warn("%s", *argv);
107				eval = 1;
108				continue;
109			}
110			if (argc > 1) {
111				(void)printf("%s==> %s <==\n",
112				    first ? "" : "\n", *argv);
113				first = 0;
114			}
115			if (bytecnt == -1)
116				head(fp, linecnt);
117			else
118				head_bytes(fp, bytecnt);
119			(void)fclose(fp);
120		}
121	} else if (bytecnt == -1)
122		head(stdin, linecnt);
123	else
124		head_bytes(stdin, bytecnt);
125
126	exit(eval);
127}
128
129static void
130head(FILE *fp, int cnt)
131{
132	char *cp;
133	size_t error, readlen;
134
135	while (cnt && (cp = fgetln(fp, &readlen)) != NULL) {
136		error = fwrite(cp, sizeof(char), readlen, stdout);
137		if (error != readlen)
138			err(1, "stdout");
139		cnt--;
140	}
141}
142
143static void
144head_bytes(FILE *fp, size_t cnt)
145{
146	char buf[4096];
147	size_t readlen;
148
149	while (cnt) {
150		if (cnt < sizeof(buf))
151			readlen = cnt;
152		else
153			readlen = sizeof(buf);
154		readlen = fread(buf, sizeof(char), readlen, fp);
155		if (readlen == 0)
156			break;
157		if (fwrite(buf, sizeof(char), readlen, stdout) != readlen)
158			err(1, "stdout");
159		cnt -= readlen;
160	}
161}
162
163static void
164obsolete(char *argv[])
165{
166	char *ap;
167
168	while ((ap = *++argv)) {
169		/* Return if "--" or not "-[0-9]*". */
170		if (ap[0] != '-' || ap[1] == '-' || !isdigit(ap[1]))
171			return;
172		if ((ap = malloc(strlen(*argv) + 2)) == NULL)
173			err(1, NULL);
174		ap[0] = '-';
175		ap[1] = 'n';
176		(void)strcpy(ap + 2, *argv + 1);
177		*argv = ap;
178	}
179}
180
181static void
182usage(void)
183{
184
185	(void)fprintf(stderr, "usage: head [-n lines | -c bytes] [file ...]\n");
186	exit(1);
187}
188