head.c revision 40114 
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
44static const char rcsid[] =
45	"$Id: head.c,v 1.8 1997/07/11 06:13:18 charnier Exp $";
46#endif /* not lint */
47
48#include <sys/types.h>
49
50#include <ctype.h>
51#include <err.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
63void head __P((FILE *, int));
64void head_bytes __P((FILE *, int));
65void obsolete __P((char *[]));
66void usage __P((void));
67
68int eval;
69
70int
71main(argc, argv)
72	int argc;
73	char *argv[];
74{
75	register int ch;
76	FILE *fp;
77	int first, linecnt = -1, bytecnt = -1;
78	char *ep;
79
80	obsolete(argv);
81	while ((ch = getopt(argc, argv, "n:c:")) != -1)
82		switch(ch) {
83		case 'c':
84			bytecnt = strtol(optarg, &ep, 10);
85			if (*ep || bytecnt <= 0)
86				errx(1, "illegal byte count -- %s", optarg);
87			break;
88		case 'n':
89			linecnt = strtol(optarg, &ep, 10);
90			if (*ep || linecnt <= 0)
91				errx(1, "illegal line count -- %s", optarg);
92			break;
93		case '?':
94		default:
95			usage();
96		}
97	argc -= optind;
98	argv += optind;
99
100	if (linecnt != -1 && bytecnt != -1)
101		errx(1, "can't combine line and byte counts");
102	if (linecnt == -1 )
103		linecnt = 10;
104	if (*argv) {
105		for (first = 1; *argv; ++argv) {
106			if ((fp = fopen(*argv, "r")) == NULL) {
107				warn("%s", *argv);
108				eval = 1;
109				continue;
110			}
111			if (argc > 1) {
112				(void)printf("%s==> %s <==\n",
113				    first ? "" : "\n", *argv);
114				first = 0;
115			}
116			if (bytecnt == -1)
117				head(fp, linecnt);
118			else
119				head_bytes(fp, bytecnt);
120			(void)fclose(fp);
121		}
122	}
123	else if (bytecnt == -1)
124		head(stdin, linecnt);
125	else
126		head_bytes(stdin, bytecnt);
127
128	exit(eval);
129}
130
131void
132head(fp, cnt)
133	FILE *fp;
134	register int cnt;
135{
136	register int ch;
137
138	while (cnt && (ch = getc(fp)) != EOF) {
139			if (putchar(ch) == EOF)
140				err(1, "stdout");
141			if (ch == '\n')
142				cnt--;
143		}
144}
145
146void
147head_bytes(fp, cnt)
148	 FILE *fp;
149	 register int cnt;
150{
151	char buf[4096];
152	register int readlen;
153
154	while (cnt) {
155		if (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
168void
169obsolete(argv)
170	char *argv[];
171{
172	char *ap;
173
174	while ((ap = *++argv)) {
175		/* Return if "--" or not "-[0-9]*". */
176		if (ap[0] != '-' || ap[1] == '-' || !isdigit(ap[1]))
177			return;
178		if ((ap = malloc(strlen(*argv) + 2)) == NULL)
179			err(1, NULL);
180		ap[0] = '-';
181		ap[1] = 'n';
182		(void)strcpy(ap + 2, *argv + 1);
183		*argv = ap;
184	}
185}
186
187void
188usage()
189{
190	(void)fprintf(stderr, "usage: head [-n lines] [-c bytes] [file ...]\n");
191	exit(1);
192}
193