1 /**
2 * collectd - src/utils_tail.c
3 * Copyright (C) 2007-2008 C-Ware, Inc.
4 * Copyright (C) 2008 Florian Forster
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the "Software"),
8 * to deal in the Software without restriction, including without limitation
9 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10 * and/or sell copies of the Software, and to permit persons to whom the
11 * Software is furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
19 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
21 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
22 * DEALINGS IN THE SOFTWARE.
23 *
24 * Author:
25 * Luke Heberling <lukeh at c-ware.com>
26 * Florian Forster <octo at collectd.org>
27 *
28 * Description:
29 * Encapsulates useful code for plugins which must watch for appends to
30 * the end of a file.
31 **/
33 #include "collectd.h"
34 #include "common.h"
35 #include "utils_tail.h"
37 struct cu_tail_s
38 {
39 char *file;
40 FILE *fh;
41 struct stat stat;
42 };
44 static int cu_tail_reopen (cu_tail_t *obj)
45 {
46 int seek_end = 0;
47 FILE *fh;
48 struct stat stat_buf;
49 int status;
51 memset (&stat_buf, 0, sizeof (stat_buf));
52 status = stat (obj->file, &stat_buf);
53 if (status != 0)
54 {
55 char errbuf[1024];
56 ERROR ("utils_tail: stat (%s) failed: %s", obj->file,
57 sstrerror (errno, errbuf, sizeof (errbuf)));
58 return (-1);
59 }
61 /* The file is already open.. */
62 if ((obj->fh != NULL) && (stat_buf.st_ino == obj->stat.st_ino))
63 {
64 /* Seek to the beginning if file was truncated */
65 if (stat_buf.st_size < obj->stat.st_size)
66 {
67 INFO ("utils_tail: File `%s' was truncated.", obj->file);
68 status = fseek (obj->fh, 0, SEEK_SET);
69 if (status != 0)
70 {
71 char errbuf[1024];
72 ERROR ("utils_tail: fseek (%s) failed: %s", obj->file,
73 sstrerror (errno, errbuf, sizeof (errbuf)));
74 fclose (obj->fh);
75 obj->fh = NULL;
76 return (-1);
77 }
78 }
79 memcpy (&obj->stat, &stat_buf, sizeof (struct stat));
80 return (1);
81 }
83 /* Seek to the end if we re-open the same file again or the file opened
84 * is the first at all or the first after an error */
85 if ((obj->stat.st_ino == 0) || (obj->stat.st_ino == stat_buf.st_ino))
86 seek_end = 1;
88 fh = fopen (obj->file, "r");
89 if (fh == NULL)
90 {
91 char errbuf[1024];
92 ERROR ("utils_tail: fopen (%s) failed: %s", obj->file,
93 sstrerror (errno, errbuf, sizeof (errbuf)));
94 return (-1);
95 }
97 if (seek_end != 0)
98 {
99 status = fseek (fh, 0, SEEK_END);
100 if (status != 0)
101 {
102 char errbuf[1024];
103 ERROR ("utils_tail: fseek (%s) failed: %s", obj->file,
104 sstrerror (errno, errbuf, sizeof (errbuf)));
105 fclose (fh);
106 return (-1);
107 }
108 }
110 if (obj->fh != NULL)
111 fclose (obj->fh);
112 obj->fh = fh;
113 memcpy (&obj->stat, &stat_buf, sizeof (struct stat));
115 return (0);
116 } /* int cu_tail_reopen */
118 cu_tail_t *cu_tail_create (const char *file)
119 {
120 cu_tail_t *obj;
122 obj = calloc (1, sizeof (*obj));
123 if (obj == NULL)
124 return (NULL);
126 obj->file = strdup (file);
127 if (obj->file == NULL)
128 {
129 free (obj);
130 return (NULL);
131 }
133 obj->fh = NULL;
135 return (obj);
136 } /* cu_tail_t *cu_tail_create */
138 int cu_tail_destroy (cu_tail_t *obj)
139 {
140 if (obj->fh != NULL)
141 fclose (obj->fh);
142 free (obj->file);
143 free (obj);
145 return (0);
146 } /* int cu_tail_destroy */
148 int cu_tail_readline (cu_tail_t *obj, char *buf, int buflen)
149 {
150 int status;
152 if (buflen < 1)
153 {
154 ERROR ("utils_tail: cu_tail_readline: buflen too small: %i bytes.",
155 buflen);
156 return (-1);
157 }
159 if (obj->fh == NULL)
160 {
161 status = cu_tail_reopen (obj);
162 if (status < 0)
163 return (status);
164 }
165 assert (obj->fh != NULL);
167 /* Try to read from the filehandle. If that succeeds, everything appears to
168 * be fine and we can return. */
169 clearerr (obj->fh);
170 if (fgets (buf, buflen, obj->fh) != NULL)
171 {
172 buf[buflen - 1] = 0;
173 return (0);
174 }
176 /* Check if we encountered an error */
177 if (ferror (obj->fh) != 0)
178 {
179 /* Jupp, error. Force `cu_tail_reopen' to reopen the file.. */
180 fclose (obj->fh);
181 obj->fh = NULL;
182 }
183 /* else: eof -> check if the file was moved away and reopen the new file if
184 * so.. */
186 status = cu_tail_reopen (obj);
187 /* error -> return with error */
188 if (status < 0)
189 return (status);
190 /* file end reached and file not reopened -> nothing more to read */
191 else if (status > 0)
192 {
193 buf[0] = 0;
194 return (0);
195 }
197 /* If we get here: file was re-opened and there may be more to read.. Let's
198 * try again. */
199 if (fgets (buf, buflen, obj->fh) != NULL)
200 {
201 buf[buflen - 1] = 0;
202 return (0);
203 }
205 if (ferror (obj->fh) != 0)
206 {
207 char errbuf[1024];
208 WARNING ("utils_tail: fgets (%s) returned an error: %s", obj->file,
209 sstrerror (errno, errbuf, sizeof (errbuf)));
210 fclose (obj->fh);
211 obj->fh = NULL;
212 return (-1);
213 }
215 /* EOf, well, apparently the new file is empty.. */
216 buf[0] = 0;
217 return (0);
218 } /* int cu_tail_readline */
220 int cu_tail_read (cu_tail_t *obj, char *buf, int buflen, tailfunc_t *callback,
221 void *data)
222 {
223 int status;
225 while (42)
226 {
227 size_t len;
229 status = cu_tail_readline (obj, buf, buflen);
230 if (status != 0)
231 {
232 ERROR ("utils_tail: cu_tail_read: cu_tail_readline "
233 "failed.");
234 break;
235 }
237 /* check for EOF */
238 if (buf[0] == 0)
239 break;
241 len = strlen (buf);
242 while (len > 0) {
243 if (buf[len - 1] != '\n')
244 break;
245 buf[len - 1] = '\0';
246 len--;
247 }
249 status = callback (data, buf, buflen);
250 if (status != 0)
251 {
252 ERROR ("utils_tail: cu_tail_read: callback returned "
253 "status %i.", status);
254 break;
255 }
256 }
258 return status;
259 } /* int cu_tail_read */