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
|
/* tailf.c -- tail a log file and then follow it
* Created: Tue Jan 9 15:49:21 1996 by faith@acm.org
* Copyright 1996, 2003 Rickard E. Faith (faith@acm.org)
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*
* less -F and tail -f cause a disk access every five seconds. This
* program avoids this problem by waiting for the file size to change.
* Hence, the file is not accessed, and the access time does not need to be
* flushed back to disk. This is sort of a "stealth" tail.
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <malloc.h>
#include <string.h>
#include <sys/stat.h>
#include <ctype.h>
#include <err.h>
#include "nls.h"
#define DEFAULT_LINES 10
static size_t filesize(const char *filename)
{
struct stat sb;
if (!stat(filename, &sb)) return sb.st_size;
return 0;
}
static void tailf(const char *filename, int lines)
{
char **buffer;
int head = 0;
int tail = 0;
FILE *str;
int i;
if (!(str = fopen(filename, "r")))
err(1, _("cannot open \"%s\" for read"), filename);
buffer = malloc(lines * sizeof(*buffer));
for (i = 0; i < lines; i++) buffer[i] = malloc(BUFSIZ + 1);
while (fgets(buffer[tail], BUFSIZ, str)) {
if (++tail >= lines) {
tail = 0;
head = 1;
}
}
if (head) {
for (i = tail; i < lines; i++) fputs(buffer[i], stdout);
for (i = 0; i < tail; i++) fputs(buffer[i], stdout);
} else {
for (i = head; i < tail; i++) fputs(buffer[i], stdout);
}
fflush(stdout);
for (i = 0; i < lines; i++) free(buffer[i]);
free(buffer);
}
int main(int argc, char **argv)
{
char buffer[BUFSIZ];
size_t osize, nsize;
FILE *str;
const char *filename;
int count, wcount;
int lines = DEFAULT_LINES;
setlocale(LC_ALL, "");
bindtextdomain(PACKAGE, LOCALEDIR);
textdomain(PACKAGE);
argc--;
argv++;
for (; argc > 0 && argv[0][0] == '-'; argc--, argv++) {
if (!strcmp(*argv, "-n") || !strcmp(*argv, "--lines")) {
argc--;
argv++;
if (argc > 0 && (lines = atoi(argv[0])) <= 0)
errx(EXIT_FAILURE, _("invalid number of lines"));
}
else if (isdigit(argv[0][1])) {
if ((lines = atoi(*argv + 1)) <= 0)
errx(EXIT_FAILURE, _("invalid number of lines"));
}
else
errx(EXIT_FAILURE, _("invalid option"));
}
if (argc != 1)
errx(EXIT_FAILURE, _("usage: tailf [-n N | -N] logfile"));
filename = argv[0];
tailf(filename, lines);
for (osize = filesize(filename);;) {
nsize = filesize(filename);
if (nsize != osize) {
if (!(str = fopen(filename, "r")))
err(EXIT_FAILURE, _("cannot open \"%s\" for read"), filename);
if (!fseek(str, osize, SEEK_SET))
while ((count = fread(buffer, 1, sizeof(buffer), str)) > 0) {
wcount = fwrite(buffer, 1, count, stdout);
if (wcount != count)
warnx(_("incomplete write to \"%s\" (written %d, expected %d)\n"),
filename, wcount, count);
}
fflush(stdout);
fclose(str);
osize = nsize;
}
usleep(250000); /* 250mS */
}
return EXIT_SUCCESS;
}
|
