1 /*
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1980, 1987, 1992, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32 #ifndef lint
33 static const char copyright[] =
34 "@(#) Copyright (c) 1980, 1987, 1992, 1993\n\
35 The Regents of the University of California. All rights reserved.\n";
36 #endif /* not lint */
37
38 #ifndef lint
39 #if 0
40 static char sccsid[] = "@(#)head.c 8.2 (Berkeley) 5/4/95";
41 #endif
42 #endif /* not lint */
43 #include <sys/cdefs.h>
44 __FBSDID("$FreeBSD: stable/12/usr.bin/head/head.c 332374 2018-04-10 14:44:07Z kevans $");
45
46 #include <sys/types.h>
47
48 #include <ctype.h>
49 #include <err.h>
50 #include <getopt.h>
51 #include <inttypes.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
63 static void head(FILE *, int);
64 static void head_bytes(FILE *, off_t);
65 static void obsolete(char *[]);
66 static void usage(void);
67
68 static const struct option long_opts[] =
69 {
70 {"bytes", required_argument, NULL, 'c'},
71 {"lines", required_argument, NULL, 'n'},
72 {NULL, no_argument, NULL, 0}
73 };
74
75 int
main(int argc,char * argv[])76 main(int argc, char *argv[])
77 {
78 int ch;
79 FILE *fp;
80 int first, linecnt = -1, eval = 0;
81 off_t bytecnt = -1;
82 char *ep;
83
84 obsolete(argv);
85 while ((ch = getopt_long(argc, argv, "+n:c:", long_opts, NULL)) != -1)
86 switch(ch) {
87 case 'c':
88 bytecnt = strtoimax(optarg, &ep, 10);
89 if (*ep || bytecnt <= 0)
90 errx(1, "illegal byte count -- %s", optarg);
91 break;
92 case 'n':
93 linecnt = strtol(optarg, &ep, 10);
94 if (*ep || linecnt <= 0)
95 errx(1, "illegal line count -- %s", optarg);
96 break;
97 case '?':
98 default:
99 usage();
100 }
101 argc -= optind;
102 argv += optind;
103
104 if (linecnt != -1 && bytecnt != -1)
105 errx(1, "can't combine line and byte counts");
106 if (linecnt == -1 )
107 linecnt = 10;
108 if (*argv) {
109 for (first = 1; *argv; ++argv) {
110 if ((fp = fopen(*argv, "r")) == NULL) {
111 warn("%s", *argv);
112 eval = 1;
113 continue;
114 }
115 if (argc > 1) {
116 (void)printf("%s==> %s <==\n",
117 first ? "" : "\n", *argv);
118 first = 0;
119 }
120 if (bytecnt == -1)
121 head(fp, linecnt);
122 else
123 head_bytes(fp, bytecnt);
124 (void)fclose(fp);
125 }
126 } else if (bytecnt == -1)
127 head(stdin, linecnt);
128 else
129 head_bytes(stdin, bytecnt);
130
131 exit(eval);
132 }
133
134 static void
head(FILE * fp,int cnt)135 head(FILE *fp, int cnt)
136 {
137 char *cp;
138 size_t error, readlen;
139
140 while (cnt && (cp = fgetln(fp, &readlen)) != NULL) {
141 error = fwrite(cp, sizeof(char), readlen, stdout);
142 if (error != readlen)
143 err(1, "stdout");
144 cnt--;
145 }
146 }
147
148 static void
head_bytes(FILE * fp,off_t cnt)149 head_bytes(FILE *fp, off_t cnt)
150 {
151 char buf[4096];
152 size_t readlen;
153
154 while (cnt) {
155 if ((uintmax_t)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
168 static void
obsolete(char * argv[])169 obsolete(char *argv[])
170 {
171 char *ap;
172
173 while ((ap = *++argv)) {
174 /* Return if "--" or not "-[0-9]*". */
175 if (ap[0] != '-' || ap[1] == '-' || !isdigit(ap[1]))
176 return;
177 if ((ap = malloc(strlen(*argv) + 2)) == NULL)
178 err(1, NULL);
179 ap[0] = '-';
180 ap[1] = 'n';
181 (void)strcpy(ap + 2, *argv + 1);
182 *argv = ap;
183 }
184 }
185
186 static void
usage(void)187 usage(void)
188 {
189
190 (void)fprintf(stderr, "usage: head [-n lines | -c bytes] [file ...]\n");
191 exit(1);
192 }
193