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DEFINITIONS
This source file includes following definitions.
- tail
- main
1 /*
2 * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
3 * The President and Fellows of Harvard College.
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 UNIVERSITY 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 UNIVERSITY 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 /*
31 * tail.c
32 *
33 * Outputs a file beginning at a specific location.
34 * Usage: tail <file> <location>
35 *
36 * This may be useful for testing during the file system assignment.
37 */
38
39 #include <unistd.h>
40 #include <stdlib.h>
41 #include <err.h>
42
43 #define BUFSIZE 1000
44
45 /* Put buffer in data space. We know that the program should allocate as */
46 /* much data space as required, but stack space is tight. */
47
48 char buffer[BUFSIZE];
49
50 static
51 void
52 tail(int file, off_t where, const char *filename)
53 {
54 int len;
55
56 if (lseek(file, where, SEEK_SET)<0) {
57 err(1, "%s", filename);
58 }
59
60 while ((len = read(file, buffer, sizeof(buffer))) > 0) {
61 write(STDOUT_FILENO, buffer, len);
62 }
63 }
64
65 int
66 main(int argc, char **argv)
67 {
68 int file;
69
70 if (argc < 3) {
71 errx(1, "Usage: tail <file> <location>");
72 }
73 file = open(argv[1], O_RDONLY);
74 if (file < 0) {
75 err(1, "%s", argv[1]);
76 }
77 tail(file, atoi(argv[2]), argv[1]);
78 close(file);
79 return 0;
80 }
81