1 /**
2 * collectd - src/utils_tail.c
3 * Copyright (C) 2007-2008 C-Ware, Inc.
4 *
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License as published by the
7 * Free Software Foundation; only version 2 of the License is applicable.
8 *
9 * This program is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License along
15 * with this program; if not, write to the Free Software Foundation, Inc.,
16 * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
17 *
18 * Author:
19 * Luke Heberling <lukeh at c-ware.com>
20 *
21 * Description:
22 * Encapsulates useful code for plugins which must watch for appends to
23 * the end of a file.
24 **/
26 #include "collectd.h"
27 #include "common.h"
28 #include "utils_tail.h"
30 struct cu_tail_s
31 {
32 char *file;
33 FILE *fd;
34 struct stat stat;
35 };
37 cu_tail_t *cu_tail_create (const char *file)
38 {
39 cu_tail_t *obj;
41 obj = (cu_tail_t *) malloc (sizeof (cu_tail_t));
42 if (obj == NULL)
43 return (NULL);
44 memset (obj, '\0', sizeof (cu_tail_t));
46 obj->file = strdup (file);
47 if (obj->file == NULL)
48 {
49 free (obj);
50 return (NULL);
51 }
53 obj->fd = NULL;
55 return (obj);
56 } /* cu_tail_t *cu_tail_create */
58 int cu_tail_destroy (cu_tail_t *obj)
59 {
60 if (obj->fd != NULL)
61 fclose (obj->fd);
62 free (obj->file);
63 free (obj);
65 return (0);
66 } /* int cu_tail_destroy */
68 int cu_tail_readline (cu_tail_t *obj, char *buf, int buflen)
69 {
70 struct stat stat_now;
71 int status;
73 if (buflen < 1)
74 return (-1);
76 if (stat (obj->file, &stat_now) != 0)
77 {
78 char errbuf[1024];
79 ERROR ("cu_tail_readline: stat (%s) failed: %s",
80 obj->file,
81 sstrerror (errno, errbuf, sizeof (errbuf)));
82 return (-1);
83 }
85 if ((stat_now.st_dev != obj->stat.st_dev) ||
86 (stat_now.st_ino != obj->stat.st_ino))
87 {
88 /*
89 * If the file was replaced open the new file and close the
90 * old filehandle
91 */
92 FILE *new_fd;
94 new_fd = fopen (obj->file, "r");
95 if (new_fd == NULL)
96 {
97 char errbuf[1024];
98 ERROR ("cu_tail_readline: open (%s) failed: %s",
99 obj->file,
100 sstrerror (errno, errbuf,
101 sizeof (errbuf)));
102 return (-1);
103 }
105 /* If there was no previous file, seek to the end. We don't
106 * want to read in the entire file, usually. */
107 if (obj->stat.st_ino == 0)
108 fseek (new_fd, 0, SEEK_END);
110 if (obj->fd != NULL)
111 fclose (obj->fd);
112 obj->fd = new_fd;
114 }
115 else if (stat_now.st_size < obj->stat.st_size)
116 {
117 /*
118 * Else, if the file was not replaces, but the file was
119 * truncated, seek to the beginning of the file.
120 */
121 assert (obj->fd != NULL);
122 rewind (obj->fd);
123 }
125 status = 0;
126 if (fgets (buf, buflen, obj->fd) == NULL)
127 {
128 if (feof (obj->fd) == 0)
129 buf[0] = '\0';
130 else /* an error occurred */
131 status = -1;
132 }
134 if (status == 0)
135 memcpy (&obj->stat, &stat_now, sizeof (struct stat));
137 return (status);
138 } /* int cu_tail_readline */
140 int cu_tail_read (cu_tail_t *obj, char *buf, int buflen, tailfunc *callback,
141 void *data)
142 {
143 int status;
145 while ((status = cu_tail_readline (obj, buf, buflen)) == 0)
146 {
147 /* check for EOF */
148 if (buf[0] == '\0')
149 break;
151 status = callback (data, buf, buflen);
152 if (status != 0)
153 break;
154 }
156 return status;
157 } /* int cu_tail_read */