head.c revision 95652 
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
46#include <sys/cdefs.h>
47__FBSDID("$FreeBSD: head/usr.bin/head/head.c 95652 2002-04-28 13:50:54Z markm $");
48
49#include <sys/types.h>
50
51#include <ctype.h>
52#include <err.h>
53#include <stdio.h>
54#include <stdlib.h>
55#include <string.h>
56#include <unistd.h>
57
58/*
59 * head - give the first few lines of a stream or of each of a set of files
60 *
61 * Bill Joy UCB August 24, 1977
62 */
63
64static void head(FILE *, int);
65static void head_bytes(FILE *, size_t);
66static void obsolete(char *[]);
67static void usage(void);
68
69int
70main(int argc, char *argv[])
71{
72	int ch;
73	FILE *fp;
74	int first, linecnt = -1, bytecnt = -1, eval = 0;
75	char *ep;
76
77	obsolete(argv);
78	while ((ch = getopt(argc, argv, "n:c:")) != -1)
79		switch(ch) {
80		case 'c':
81			bytecnt = strtol(optarg, &ep, 10);
82			if (*ep || bytecnt <= 0)
83				errx(1, "illegal byte count -- %s", optarg);
84			break;
85		case 'n':
86			linecnt = strtol(optarg, &ep, 10);
87			if (*ep || linecnt <= 0)
88				errx(1, "illegal line count -- %s", optarg);
89			break;
90		case '?':
91		default:
92			usage();
93		}
94	argc -= optind;
95	argv += optind;
96
97	if (linecnt != -1 && bytecnt != -1)
98		errx(1, "can't combine line and byte counts");
99	if (linecnt == -1 )
100		linecnt = 10;
101	if (*argv) {
102		for (first = 1; *argv; ++argv) {
103			if ((fp = fopen(*argv, "r")) == NULL) {
104				warn("%s", *argv);
105				eval = 1;
106				continue;
107			}
108			if (argc > 1) {
109				(void)printf("%s==> %s <==\n",
110				    first ? "" : "\n", *argv);
111				first = 0;
112			}
113			if (bytecnt == -1)
114				head(fp, linecnt);
115			else
116				head_bytes(fp, bytecnt);
117			(void)fclose(fp);
118		}
119	} else if (bytecnt == -1)
120		head(stdin, linecnt);
121	else
122		head_bytes(stdin, bytecnt);
123
124	exit(eval);
125}
126
127static void
128head(FILE *fp, int cnt)
129{
130	char *cp;
131	size_t error, readlen;
132
133	while (cnt && (cp = fgetln(fp, &readlen)) != NULL) {
134		error = fwrite(cp, sizeof(char), readlen, stdout);
135		if (error != readlen)
136			err(1, "stdout");
137		cnt--;
138	}
139}
140
141static void
142head_bytes(FILE *fp, size_t cnt)
143{
144	char buf[4096];
145	size_t readlen;
146
147	while (cnt) {
148		if (cnt < sizeof(buf))
149			readlen = cnt;
150		else
151			readlen = sizeof(buf);
152		readlen = fread(buf, sizeof(char), readlen, fp);
153		if (readlen == 0)
154			break;
155		if (fwrite(buf, sizeof(char), readlen, stdout) != readlen)
156			err(1, "stdout");
157		cnt -= readlen;
158	}
159}
160
161static void
162obsolete(char *argv[])
163{
164	char *ap;
165
166	while ((ap = *++argv)) {
167		/* Return if "--" or not "-[0-9]*". */
168		if (ap[0] != '-' || ap[1] == '-' || !isdigit(ap[1]))
169			return;
170		if ((ap = malloc(strlen(*argv) + 2)) == NULL)
171			err(1, NULL);
172		ap[0] = '-';
173		ap[1] = 'n';
174		(void)strcpy(ap + 2, *argv + 1);
175		*argv = ap;
176	}
177}
178
179static void
180usage(void)
181{
182
183	(void)fprintf(stderr, "usage: head [-n lines | -c bytes] [file ...]\n");
184	exit(1);
185}
186