1 /*-
2 * Copyright (c) 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Edward Sze-Tyan Wang.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * @(#)forward.c 8.1 (Berkeley) 6/6/93
33 * $FreeBSD: src/usr.bin/tail/forward.c,v 1.11.6.7 2003/01/07 05:26:22 tjr Exp $
34 */
35
36 #include <sys/types.h>
37 #include <sys/stat.h>
38 #include <sys/time.h>
39 #include <sys/mman.h>
40 #ifndef BOOTSTRAPPING
41 #include <sys/event.h>
42 #endif
43
44 #include <limits.h>
45 #include <fcntl.h>
46 #include <errno.h>
47 #include <unistd.h>
48 #include <stdio.h>
49 #include <stdlib.h>
50 #include <string.h>
51 #include <err.h>
52 #include "extern.h"
53
54 static void rlines(FILE *, off_t, struct stat *);
55
56 /* defines for inner loop actions */
57 #define USE_SLEEP 0
58 #ifndef BOOTSTRAPPING
59 #define USE_KQUEUE 1
60 #define ADD_EVENTS 2
61
62 struct kevent *ev;
63 #endif
64 int action = USE_SLEEP;
65 int kq;
66
67 /*
68 * forward -- display the file, from an offset, forward.
69 *
70 * There are eight separate cases for this -- regular and non-regular
71 * files, by bytes or lines and from the beginning or end of the file.
72 *
73 * FBYTES byte offset from the beginning of the file
74 * REG seek
75 * NOREG read, counting bytes
76 *
77 * FLINES line offset from the beginning of the file
78 * REG read, counting lines
79 * NOREG read, counting lines
80 *
81 * RBYTES byte offset from the end of the file
82 * REG seek
83 * NOREG cyclically read characters into a wrap-around buffer
84 *
85 * RLINES
86 * REG mmap the file and step back until reach the correct offset.
87 * NOREG cyclically read lines into a wrap-around array of buffers
88 */
89 void
forward(FILE * fp,enum STYLE style,off_t off,struct stat * sbp)90 forward(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
91 {
92 int ch;
93
94 switch(style) {
95 case FBYTES:
96 if (off == 0)
97 break;
98 if (S_ISREG(sbp->st_mode)) {
99 if (sbp->st_size < off)
100 off = sbp->st_size;
101 if (fseeko(fp, off, SEEK_SET) == -1) {
102 ierr();
103 return;
104 }
105 } else while (off--)
106 if ((ch = getc(fp)) == EOF) {
107 if (ferror(fp)) {
108 ierr();
109 return;
110 }
111 break;
112 }
113 break;
114 case FLINES:
115 if (off == 0)
116 break;
117 for (;;) {
118 if ((ch = getc(fp)) == EOF) {
119 if (ferror(fp)) {
120 ierr();
121 return;
122 }
123 break;
124 }
125 if (ch == '\n' && !--off)
126 break;
127 }
128 break;
129 case RBYTES:
130 if (S_ISREG(sbp->st_mode)) {
131 if (sbp->st_size >= off &&
132 fseeko(fp, -off, SEEK_END) == -1) {
133 ierr();
134 return;
135 }
136 } else if (off == 0) {
137 while (getc(fp) != EOF);
138 if (ferror(fp)) {
139 ierr();
140 return;
141 }
142 } else
143 if (display_bytes(fp, off))
144 return;
145 break;
146 case RLINES:
147 if (S_ISREG(sbp->st_mode) && sbp->st_size != 0)
148 if (!off) {
149 if (fseeko(fp, (off_t)0, SEEK_END) == -1) {
150 ierr();
151 return;
152 }
153 } else
154 rlines(fp, off, sbp);
155 else if (off == 0) {
156 while (getc(fp) != EOF);
157 if (ferror(fp)) {
158 ierr();
159 return;
160 }
161 } else
162 if (display_lines(fp, off))
163 return;
164 break;
165 case REVERSE:
166 errx(1, "internal error: forward style cannot be REVERSE");
167 /* NOTREACHED */
168 }
169
170 while ((ch = getc(fp)) != EOF) {
171 if (putchar(ch) == EOF)
172 oerr();
173 }
174 if (ferror(fp)) {
175 ierr();
176 return;
177 }
178 fflush(stdout);
179 }
180
181 /*
182 * rlines -- display the last offset lines of the file.
183 */
184 static void
rlines(FILE * fp,off_t off,struct stat * sbp)185 rlines(FILE *fp, off_t off, struct stat *sbp)
186 {
187 struct mapinfo map;
188 off_t curoff, size;
189 int i;
190
191 if (!(size = sbp->st_size))
192 return;
193 map.start = NULL;
194 map.fd = fileno(fp);
195 map.mapoff = map.maxoff = size;
196
197 /*
198 * Last char is special, ignore whether newline or not. Note that
199 * size == 0 is dealt with above, and size == 1 sets curoff to -1.
200 */
201 curoff = size - 2;
202 while (curoff >= 0) {
203 if (curoff < map.mapoff && maparound(&map, curoff) != 0) {
204 ierr();
205 return;
206 }
207 for (i = curoff - map.mapoff; i >= 0; i--)
208 if (map.start[i] == '\n' && --off == 0)
209 break;
210 /* `i' is either the map offset of a '\n', or -1. */
211 curoff = map.mapoff + i;
212 if (i >= 0)
213 break;
214 }
215 curoff++;
216 if (mapprint(&map, curoff, size - curoff) != 0) {
217 ierr();
218 exit(1);
219 }
220
221 /* Set the file pointer to reflect the length displayed. */
222 if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) {
223 ierr();
224 return;
225 }
226 if (map.start != NULL && munmap(map.start, map.maplen)) {
227 ierr();
228 return;
229 }
230 }
231
232 /*
233 * follow -- display the file, from an offset, forward.
234 */
235 #ifndef BOOTSTRAPPING
236 static void
show(file_info_t * file,int at_index)237 show(file_info_t *file, int at_index)
238 {
239 int ch, first;
240
241 first = 1;
242 while ((ch = getc(file->fp)) != EOF) {
243 if (first && no_files > 1) {
244 showfilename(at_index, file->file_name);
245 first = 0;
246 }
247 if (putchar(ch) == EOF)
248 oerr();
249 }
250 fflush(stdout);
251 if (ferror(file->fp)) {
252 file->fp = NULL;
253 ierr();
254 } else {
255 clearerr(file->fp);
256 }
257 }
258 #endif
259
260 void
showfilename(int at_index,const char * filename)261 showfilename(int at_index, const char *filename)
262 {
263 static int last_index = -1;
264 static int continuing = 0;
265
266 if (last_index == at_index)
267 return;
268 if (!qflag) {
269 if (continuing)
270 printf("\n");
271 printf("==> %s <==\n", filename);
272 }
273 continuing = 1;
274 last_index = at_index;
275 }
276
277 #ifndef BOOTSTRAPPING
278 static void
set_events(file_info_t * files)279 set_events(file_info_t *files)
280 {
281 int i, n;
282 file_info_t *file;
283 struct timespec ts;
284
285 ts.tv_sec = 0;
286 ts.tv_nsec = 0;
287
288 n = 0;
289 action = USE_KQUEUE;
290 for (i = 0, file = files; i < no_files; i++, file++) {
291 if (file->fp == NULL)
292 continue;
293 if (Fflag && fileno(file->fp) != STDIN_FILENO) {
294 EV_SET(&ev[n], fileno(file->fp), EVFILT_VNODE,
295 EV_ADD | EV_ENABLE | EV_CLEAR,
296 NOTE_DELETE | NOTE_RENAME, 0, 0);
297 n++;
298 }
299 EV_SET(&ev[n], fileno(file->fp), EVFILT_READ,
300 EV_ADD | EV_ENABLE | EV_CLEAR, 0, 0, 0);
301 n++;
302 }
303
304 if (kevent(kq, ev, n, NULL, 0, &ts) < 0)
305 action = USE_SLEEP;
306 }
307
308 void
follow(file_info_t * files,enum STYLE style,off_t off)309 follow(file_info_t *files, enum STYLE style, off_t off)
310 {
311 int active, i, n;
312 file_info_t *file;
313 struct stat sb2;
314 struct timespec ts;
315
316 /* Position each of the files */
317 file = files;
318 active = 0;
319 n = 0;
320 for (i = 0; i < no_files; i++, file++) {
321 if (file->fp) {
322 active = 1;
323 n++;
324 if (vflag || no_files > 1)
325 showfilename(i, file->file_name);
326 forward(file->fp, style, off, &file->st);
327 if (Fflag && fileno(file->fp) != STDIN_FILENO)
328 n++;
329 }
330 }
331
332 if (!active)
333 return;
334
335 kq = kqueue();
336 if (kq == -1)
337 err(1, "kqueue");
338 ev = malloc(n * sizeof(struct kevent));
339 if (ev == NULL)
340 err(1, "Couldn't allocate memory for kevents.");
341 set_events(files);
342
343 for (;;) {
344 for (i = 0, file = files; i < no_files; i++, file++) {
345 if (file->fp == NULL)
346 continue;
347 if (Fflag && fileno(file->fp) != STDIN_FILENO) {
348 if (stat(file->file_name, &sb2) == -1) {
349 /*
350 * file was rotated, skip it until it
351 * reappears.
352 */
353 continue;
354 }
355 if (sb2.st_ino != file->st.st_ino ||
356 sb2.st_dev != file->st.st_dev ||
357 sb2.st_nlink == 0) {
358 file->fp = freopen(file->file_name, "r",
359 file->fp);
360 if (file->fp == NULL) {
361 ierr();
362 continue;
363 } else {
364 memcpy(&file->st, &sb2,
365 sizeof(struct stat));
366 set_events(files);
367 }
368 }
369 }
370 show(file, i);
371 }
372
373 switch (action) {
374 case USE_KQUEUE:
375 ts.tv_sec = 1;
376 ts.tv_nsec = 0;
377 /*
378 * In the -F case, we set a timeout to ensure that
379 * we re-stat the file at least once every second.
380 */
381 n = kevent(kq, NULL, 0, ev, 1, Fflag ? &ts : NULL);
382 if (n == -1)
383 err(1, "kevent");
384 if (n == 0) {
385 /* timeout */
386 break;
387 } else if (ev->filter == EVFILT_READ && ev->data < 0) {
388 /* file shrank, reposition to end */
389 if (lseek(ev->ident, 0, SEEK_END) == -1) {
390 ierr();
391 continue;
392 }
393 }
394 break;
395
396 case USE_SLEEP:
397 usleep(250000);
398 break;
399 }
400 }
401 }
402 #endif
403