1 /* $OpenBSD: head.c,v 1.24 2022/02/07 17:19:57 cheloha Exp $ */
2
3 /*
4 * Copyright (c) 1980, 1987 Regents of the University of California.
5 * 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 #include <stdio.h>
33 #include <stdlib.h>
34 #include <ctype.h>
35 #include <limits.h>
36 #include <err.h>
37 #include <errno.h>
38 #include <unistd.h>
39
40 int head_file(const char *, long, int);
41 static void usage(void);
42
43 /*
44 * head - give the first few lines of a stream or of each of a set of files
45 *
46 * Bill Joy UCB August 24, 1977
47 */
48
49 int
main(int argc,char * argv[])50 main(int argc, char *argv[])
51 {
52 const char *errstr;
53 int ch;
54 long linecnt = 10;
55 int status = 0;
56
57 if (pledge("stdio rpath", NULL) == -1)
58 err(1, "pledge");
59
60 /* handle obsolete -number syntax */
61 if (argc > 1 && argv[1][0] == '-' &&
62 isdigit((unsigned char)argv[1][1])) {
63 linecnt = strtonum(argv[1] + 1, 1, LONG_MAX, &errstr);
64 if (errstr != NULL)
65 errx(1, "count is %s: %s", errstr, argv[1] + 1);
66 argc--;
67 argv++;
68 }
69
70 while ((ch = getopt(argc, argv, "n:")) != -1) {
71 switch (ch) {
72 case 'n':
73 linecnt = strtonum(optarg, 1, LONG_MAX, &errstr);
74 if (errstr != NULL)
75 errx(1, "count is %s: %s", errstr, optarg);
76 break;
77 default:
78 usage();
79 }
80 }
81 argc -= optind, argv += optind;
82
83 if (argc == 0) {
84 if (pledge("stdio", NULL) == -1)
85 err(1, "pledge");
86
87 status = head_file(NULL, linecnt, 0);
88 } else {
89 for (; *argv != NULL; argv++)
90 status |= head_file(*argv, linecnt, argc > 1);
91 }
92
93 return status;
94 }
95
96 int
head_file(const char * path,long count,int need_header)97 head_file(const char *path, long count, int need_header)
98 {
99 const char *name;
100 FILE *fp;
101 int ch, status = 0;
102 static int first = 1;
103
104 if (path != NULL) {
105 name = path;
106 fp = fopen(name, "r");
107 if (fp == NULL) {
108 warn("%s", name);
109 return 1;
110 }
111 if (need_header) {
112 printf("%s==> %s <==\n", first ? "" : "\n", name);
113 if (ferror(stdout))
114 err(1, "stdout");
115 first = 0;
116 }
117 } else {
118 name = "stdin";
119 fp = stdin;
120 }
121
122 while ((ch = getc(fp)) != EOF) {
123 if (putchar(ch) == EOF)
124 err(1, "stdout");
125 if (ch == '\n' && --count == 0)
126 break;
127 }
128 if (ferror(fp)) {
129 warn("%s", name);
130 status = 1;
131 }
132
133 fclose(fp);
134
135 return status;
136 }
137
138
139 static void
usage(void)140 usage(void)
141 {
142 fputs("usage: head [-count | -n count] [file ...]\n", stderr);
143 exit(1);
144 }
145