head.c revision 10064 
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 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
41static char sccsid[] = "@(#)head.c	8.1 (Berkeley) 6/6/93";
42#endif /* not lint */
43
44#include <sys/types.h>
45#include <errno.h>
46#include <stdlib.h>
47#include <string.h>
48#include <stdio.h>
49#include <ctype.h>
50
51/*
52 * head - give the first few lines of a stream or of each of a set of files
53 *
54 * Bill Joy UCB August 24, 1977
55 */
56
57void err __P((int, const char *, ...));
58void head __P((FILE *, int));
59void obsolete __P((char *[]));
60void usage __P((void));
61
62int eval;
63
64int
65main(argc, argv)
66	int argc;
67	char *argv[];
68{
69	register int ch;
70	FILE *fp;
71	int first, linecnt;
72	char *ep;
73
74	obsolete(argv);
75	linecnt = 10;
76	while ((ch = getopt(argc, argv, "n:")) != EOF)
77		switch(ch) {
78		case 'n':
79			linecnt = strtol(optarg, &ep, 10);
80			if (*ep || linecnt <= 0)
81				err(1, "illegal line count -- %s", optarg);
82			break;
83		case '?':
84		default:
85			usage();
86		}
87	argc -= optind;
88	argv += optind;
89
90	if (*argv)
91		for (first = 1; *argv; ++argv) {
92			if ((fp = fopen(*argv, "r")) == NULL) {
93				err(0, "%s: %s", *argv, strerror(errno));
94				continue;
95			}
96			if (argc > 1) {
97				(void)printf("%s==> %s <==\n",
98				    first ? "" : "\n", *argv);
99				first = 0;
100			}
101			head(fp, linecnt);
102			(void)fclose(fp);
103		}
104	else
105		head(stdin, linecnt);
106	exit(eval);
107}
108
109void
110head(fp, cnt)
111	FILE *fp;
112	register int cnt;
113{
114	register int ch;
115
116	while ((ch = getc(fp)) != EOF && cnt) {
117			if (putchar(ch) == EOF)
118				err(1, "stdout: %s", strerror(errno));
119			if (ch == '\n')
120				cnt--;
121		}
122}
123
124void
125obsolete(argv)
126	char *argv[];
127{
128	char *ap;
129
130	while (ap = *++argv) {
131		/* Return if "--" or not "-[0-9]*". */
132		if (ap[0] != '-' || ap[1] == '-' || !isdigit(ap[1]))
133			return;
134		if ((ap = malloc(strlen(*argv) + 2)) == NULL)
135			err(1, "%s", strerror(errno));
136		ap[0] = '-';
137		ap[1] = 'n';
138		(void)strcpy(ap + 2, *argv + 1);
139		*argv = ap;
140	}
141}
142
143void
144usage()
145{
146	(void)fprintf(stderr, "usage: head [-n lines] [file ...]\n");
147	exit(1);
148}
149
150#if __STDC__
151#include <stdarg.h>
152#else
153#include <varargs.h>
154#endif
155
156void
157#if __STDC__
158err(int fatal, const char *fmt, ...)
159#else
160err(fatal, fmt, va_alist)
161	int fatal;
162	char *fmt;
163        va_dcl
164#endif
165{
166	va_list ap;
167#if __STDC__
168	va_start(ap, fmt);
169#else
170	va_start(ap);
171#endif
172	(void)fprintf(stderr, "head: ");
173	(void)vfprintf(stderr, fmt, ap);
174	va_end(ap);
175	(void)fprintf(stderr, "\n");
176	if (fatal)
177		exit(1);
178	eval = 1;
179}
180