1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
|
/*
* extend.c --- extend a file so that it has at least a specified
* number of blocks.
*
* Copyright (C) 1993, 1994, 1995 Theodore Ts'o.
*
* This file may be redistributed under the terms of the GNU Public
* License.
*/
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <fcntl.h>
static void usage(char *progname)
{
fprintf(stderr, "%s: %s filename nblocks blocksize\n",
progname, progname);
exit(1);
}
int main(int argc, char **argv)
{
char *filename;
int nblocks, blocksize;
int fd;
char *block;
int ret;
if (argc != 4)
usage(argv[0]);
filename = argv[1];
nblocks = strtoul(argv[2], 0, 0) - 1;
blocksize = strtoul(argv[3], 0, 0);
if (nblocks < 0) {
fprintf(stderr, "Illegal number of blocks!\n");
exit(1);
}
block = malloc(blocksize);
if (block == 0) {
fprintf(stderr, "Couldn't allocate block buffer(size=%d)\n",
blocksize);
exit(1);
}
memset(block, 0, blocksize);
fd = open(filename, O_RDWR);
if (fd < 0) {
perror(filename);
exit(1);
}
ret = lseek(fd, nblocks*blocksize, SEEK_SET);
if (ret < 0) {
perror("lseek");
exit(1);
}
ret = read(fd, block, blocksize);
if (ret < 0) {
perror("read");
exit(1);
}
ret = lseek(fd, nblocks*blocksize, SEEK_SET);
if (ret < 0) {
perror("lseek #2");
exit(1);
}
ret = write(fd, block, blocksize);
if (ret < 0) {
perror("read");
exit(1);
}
exit(0);
}
|
