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
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
|
/*
* simpletail.c
* A fast implementation of tail which uses the inotify-API present in
* recent Linux Kernels.
*
* Copyright (C) 2005-2006, Tobias Klauser <tklauser@access.unizh.ch>
*
* The idea and some code were taken from turbotail.
*
* This program is free software; you can redistribute it and/or modify it under
* the terms of the GNU General Public License as published by the Free Software
* Foundation; either version 2, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc., 51
* Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include "inotify.h"
#include "inotify-syscalls.h"
#include "inotail.h"
#define BUFFER_SIZE 4096
#define DEFAULT_N_LINES 10
void usage(void)
{
fprintf(stderr, "usage: simpletail [-f] [-n <nr-lines>] <file>\n");
exit(EXIT_FAILURE);
}
off_t lines(int fd, int file_size, unsigned int n_lines)
{
int i;
char buf[BUFFER_SIZE];
off_t offset = file_size;
/* Negative offsets don't make sense here */
if (offset < 0)
offset = 0;
n_lines += 1; /* We also count the last \n */
while (offset > 0 && n_lines > 0) {
int rc;
int block_size = BUFFER_SIZE; /* Size of the current block we're reading */
if (offset < BUFFER_SIZE)
block_size = offset;
/* Start of current block */
offset -= block_size;
dprintf(" offset: %lu\n", offset);
lseek(fd, offset, SEEK_SET);
rc = read(fd, &buf, block_size);
for (i = block_size; i > 0; i--) {
if (buf[i] == '\n') {
dprintf(" Found \\n at position %d\n", i);
n_lines--;
if (n_lines == 0)
break;
}
}
}
if (n_lines == 0)
offset += i + 1; /* We don't want the first \n */
return offset;
}
int watch_file(const char *filename, off_t offset)
{
int ifd, watch;
struct inotify_event *inev;
char buf[BUFFER_SIZE];
dprintf(">> Watching %s\n", filename);
ifd = inotify_init();
if (ifd < 0) {
perror("inotify_init()");
exit(-2);
}
watch = inotify_add_watch(ifd, filename, IN_MODIFY|IN_DELETE_SELF|IN_MOVE_SELF|IN_UNMOUNT);
memset(&buf, 0, sizeof(buf));
while (1) {
int len;
len = read(ifd, buf, sizeof(buf));
inev = (struct inotify_event *) &buf;
while (len > 0) {
if (inev->mask & IN_MODIFY) {
int ffd, block_size;
char fbuf[BUFFER_SIZE];
struct stat finfo;
dprintf(" File '%s' modified.\n", filename);
dprintf(" offset: %lu.\n", offset);
ffd = open(filename, O_RDONLY);
if (fstat(ffd, &finfo) < 0) {
perror("fstat()");
return -1;
}
/* XXX: block_size could be bigger than BUFFER_SIZE */
block_size = finfo.st_size - offset;
if (block_size < 0)
block_size = 0;
lseek(ffd, offset, SEEK_SET);
while (read(ffd, &fbuf, BUFFER_SIZE) != 0) {
write(STDOUT_FILENO, fbuf, block_size);
}
offset = finfo.st_size;
close(ffd);
}
if (inev->mask & IN_DELETE_SELF) {
dprintf(" File '%s' deleted.\n", filename);
return -1;
}
if (inev->mask & IN_MOVE_SELF) {
dprintf(" File '%s' moved.\n", filename);
return -1;
}
if (inev->mask & IN_UNMOUNT) {
dprintf(" Device containing file '%s' unmounted.\n", filename);
return -1;
}
len -= sizeof(struct inotify_event) + inev->len;
inev = (struct inotify_event *) ((char *) inev + sizeof(struct inotify_event) + inev->len);
}
}
}
int main(int argc, char **argv)
{
int i, fd;
int n_lines = DEFAULT_N_LINES;
int ret = 0;
short forever = 0;
char buf[BUFFER_SIZE], *filename;
struct stat finfo;
off_t offset = 0;
if (argc < 2)
usage();
for (i = 1; (i + 1 < argc) && (argv[i][0] == '-'); i++) {
switch (argv[i][1]) {
case 'f':
forever = 1;
break;
case 'n':
n_lines = strtol(argv[++i], NULL, 0);
break;
default:
usage();
break;
}
}
filename = argv[i];
fd = open(filename, O_RDONLY);
if (fd < 0) {
perror("open()");
return -1;
}
if (fstat(fd, &finfo) < 0) {
perror("fstat()");
return -1;
}
offset = lines(fd, finfo.st_size, n_lines);
dprintf(" offset: %lu.\n", offset);
lseek(fd, offset, SEEK_SET);
while (read(fd, &buf, BUFFER_SIZE) != 0) {
write(STDOUT_FILENO, buf, finfo.st_size - offset);
}
close(fd);
if (forever)
ret = watch_file(filename, finfo.st_size);
return ret;
}
|
