xref: /freebsd/usr.bin/head/head.c (revision a35f04fba2ebb8f86d4cbdc710c89a094572b08e)
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. Neither the name of the University nor the names of its contributors
14  *    may be used to endorse or promote products derived from this software
15  *    without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  */
29 
30 #ifndef lint
31 static const char copyright[] =
32 "@(#) Copyright (c) 1980, 1987, 1992, 1993\n\
33 	The Regents of the University of California.  All rights reserved.\n";
34 #endif /* not lint */
35 
36 #ifndef lint
37 #if 0
38 static char sccsid[] = "@(#)head.c	8.2 (Berkeley) 5/4/95";
39 #endif
40 #endif /* not lint */
41 #include <sys/cdefs.h>
42 __FBSDID("$FreeBSD$");
43 
44 #include <sys/types.h>
45 
46 #include <ctype.h>
47 #include <err.h>
48 #include <inttypes.h>
49 #include <stdio.h>
50 #include <stdlib.h>
51 #include <string.h>
52 #include <unistd.h>
53 
54 /*
55  * head - give the first few lines of a stream or of each of a set of files
56  *
57  * Bill Joy UCB August 24, 1977
58  */
59 
60 static void head(FILE *, int);
61 static void head_bytes(FILE *, off_t);
62 static void obsolete(char *[]);
63 static void usage(void);
64 
65 int
66 main(int argc, char *argv[])
67 {
68 	int ch;
69 	FILE *fp;
70 	int first, linecnt = -1, eval = 0;
71 	off_t bytecnt = -1;
72 	char *ep;
73 
74 	obsolete(argv);
75 	while ((ch = getopt(argc, argv, "n:c:")) != -1)
76 		switch(ch) {
77 		case 'c':
78 			bytecnt = strtoimax(optarg, &ep, 10);
79 			if (*ep || bytecnt <= 0)
80 				errx(1, "illegal byte count -- %s", optarg);
81 			break;
82 		case 'n':
83 			linecnt = strtol(optarg, &ep, 10);
84 			if (*ep || linecnt <= 0)
85 				errx(1, "illegal line count -- %s", optarg);
86 			break;
87 		case '?':
88 		default:
89 			usage();
90 		}
91 	argc -= optind;
92 	argv += optind;
93 
94 	if (linecnt != -1 && bytecnt != -1)
95 		errx(1, "can't combine line and byte counts");
96 	if (linecnt == -1 )
97 		linecnt = 10;
98 	if (*argv) {
99 		for (first = 1; *argv; ++argv) {
100 			if ((fp = fopen(*argv, "r")) == NULL) {
101 				warn("%s", *argv);
102 				eval = 1;
103 				continue;
104 			}
105 			if (argc > 1) {
106 				(void)printf("%s==> %s <==\n",
107 				    first ? "" : "\n", *argv);
108 				first = 0;
109 			}
110 			if (bytecnt == -1)
111 				head(fp, linecnt);
112 			else
113 				head_bytes(fp, bytecnt);
114 			(void)fclose(fp);
115 		}
116 	} else if (bytecnt == -1)
117 		head(stdin, linecnt);
118 	else
119 		head_bytes(stdin, bytecnt);
120 
121 	exit(eval);
122 }
123 
124 static void
125 head(FILE *fp, int cnt)
126 {
127 	char *cp;
128 	size_t error, readlen;
129 
130 	while (cnt && (cp = fgetln(fp, &readlen)) != NULL) {
131 		error = fwrite(cp, sizeof(char), readlen, stdout);
132 		if (error != readlen)
133 			err(1, "stdout");
134 		cnt--;
135 	}
136 }
137 
138 static void
139 head_bytes(FILE *fp, off_t cnt)
140 {
141 	char buf[4096];
142 	size_t readlen;
143 
144 	while (cnt) {
145 		if ((uintmax_t)cnt < sizeof(buf))
146 			readlen = cnt;
147 		else
148 			readlen = sizeof(buf);
149 		readlen = fread(buf, sizeof(char), readlen, fp);
150 		if (readlen == 0)
151 			break;
152 		if (fwrite(buf, sizeof(char), readlen, stdout) != readlen)
153 			err(1, "stdout");
154 		cnt -= readlen;
155 	}
156 }
157 
158 static void
159 obsolete(char *argv[])
160 {
161 	char *ap;
162 
163 	while ((ap = *++argv)) {
164 		/* Return if "--" or not "-[0-9]*". */
165 		if (ap[0] != '-' || ap[1] == '-' || !isdigit(ap[1]))
166 			return;
167 		if ((ap = malloc(strlen(*argv) + 2)) == NULL)
168 			err(1, NULL);
169 		ap[0] = '-';
170 		ap[1] = 'n';
171 		(void)strcpy(ap + 2, *argv + 1);
172 		*argv = ap;
173 	}
174 }
175 
176 static void
177 usage(void)
178 {
179 
180 	(void)fprintf(stderr, "usage: head [-n lines | -c bytes] [file ...]\n");
181 	exit(1);
182 }
183