1 /* $OpenBSD: forward.c,v 1.20 2004/03/12 19:40:05 otto Exp $ */
2 /* $NetBSD: forward.c,v 1.7 1996/02/13 16:49:10 ghudson Exp $ */
3
4 /*-
5 * Copyright (c) 1991, 1993
6 * The Regents of the University of California. All rights reserved.
7 *
8 * This code is derived from software contributed to Berkeley by
9 * Edward Sze-Tyan Wang.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. Neither the name of the University nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36 #ifndef lint
37 #if 0
38 static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93";
39 #endif
40 static char rcsid[] = "$OpenBSD: forward.c,v 1.20 2004/03/12 19:40:05 otto Exp $";
41 #endif /* not lint */
42
43 #include <sys/types.h>
44 #include <sys/stat.h>
45 #include <sys/mman.h>
46 #include <sys/event.h>
47
48 #include <err.h>
49 #include <errno.h>
50 #include <fcntl.h>
51 #include <limits.h>
52 #include <stdio.h>
53 #include <stdlib.h>
54 #include <string.h>
55 #include <unistd.h>
56
57 #include "extern.h"
58
59 static int rlines(FILE *, off_t, struct stat *);
60
61 /*
62 * forward -- display the file, from an offset, forward.
63 *
64 * There are eight separate cases for this -- regular and non-regular
65 * files, by bytes or lines and from the beginning or end of the file.
66 *
67 * FBYTES byte offset from the beginning of the file
68 * REG seek
69 * NOREG read, counting bytes
70 *
71 * FLINES line offset from the beginning of the file
72 * REG read, counting lines
73 * NOREG read, counting lines
74 *
75 * RBYTES byte offset from the end of the file
76 * REG seek
77 * NOREG cyclically read characters into a wrap-around buffer
78 *
79 * RLINES
80 * REG step back until the correct offset is reached.
81 * NOREG cyclically read lines into a wrap-around array of buffers
82 */
83 void
forward(fp,style,off,sbp)84 forward(fp, style, off, sbp)
85 FILE *fp;
86 enum STYLE style;
87 off_t off;
88 struct stat *sbp;
89 {
90 int ch;
91 struct stat nsb;
92 int kq, queue;
93 struct kevent ke;
94
95 switch(style) {
96 case FBYTES:
97 if (off == 0)
98 break;
99 if (S_ISREG(sbp->st_mode)) {
100 if (sbp->st_size < off)
101 off = sbp->st_size;
102 if (fseeko(fp, off, SEEK_SET) == -1) {
103 ierr();
104 return;
105 }
106 } else while (off--)
107 if ((ch = getc(fp)) == EOF) {
108 if (ferror(fp)) {
109 ierr();
110 return;
111 }
112 break;
113 }
114 break;
115 case FLINES:
116 if (off == 0)
117 break;
118 for (;;) {
119 if ((ch = getc(fp)) == EOF) {
120 if (ferror(fp)) {
121 ierr();
122 return;
123 }
124 break;
125 }
126 if (ch == '\n' && !--off)
127 break;
128 }
129 break;
130 case RBYTES:
131 if (S_ISREG(sbp->st_mode)) {
132 if (sbp->st_size >= off &&
133 fseeko(fp, -off, SEEK_END) == -1) {
134 ierr();
135 return;
136 }
137 } else if (off == 0) {
138 while (getc(fp) != EOF)
139 ;
140 if (ferror(fp)) {
141 ierr();
142 return;
143 }
144 } else {
145 if (bytes(fp, off))
146 return;
147 }
148 break;
149 case RLINES:
150 if (S_ISREG(sbp->st_mode)) {
151 if (!off) {
152 if (fseeko(fp, (off_t)0, SEEK_END) == -1) {
153 ierr();
154 return;
155 }
156 } else if (rlines(fp, off, sbp) != 0)
157 lines(fp, off);
158 } else if (off == 0) {
159 while (getc(fp) != EOF)
160 ;
161 if (ferror(fp)) {
162 ierr();
163 return;
164 }
165 } else {
166 if (lines(fp, off))
167 return;
168 }
169 break;
170 }
171
172 kq = -1;
173 kq_retry:
174 if (fflag && ((kq = kqueue()) >= 0)) {
175 ke.ident = fileno(fp);
176 ke.flags = EV_ENABLE|EV_ADD|EV_CLEAR;
177 ke.filter = EVFILT_READ;
178 ke.fflags = ke.data = 0;
179 ke.udata = NULL;
180 if (kevent(kq, &ke, 1, NULL, 0, NULL) < 0) {
181 close(kq);
182 kq = -1;
183 } else if (S_ISREG(sbp->st_mode)) {
184 ke.ident = fileno(fp);
185 ke.flags = EV_ENABLE|EV_ADD|EV_CLEAR;
186 ke.filter = EVFILT_VNODE;
187 ke.fflags = NOTE_DELETE | NOTE_RENAME | NOTE_TRUNCATE;
188 if (kevent(kq, &ke, 1, NULL, 0, NULL) < 0) {
189 close(kq);
190 kq = -1;
191 }
192 }
193 }
194
195 for (;;) {
196 while (!feof(fp) && (ch = getc(fp)) != EOF)
197 if (putchar(ch) == EOF)
198 oerr();
199 if (ferror(fp)) {
200 ierr();
201 if (kq != -1)
202 close(kq);
203 return;
204 }
205 (void)fflush(stdout);
206 if (!fflag)
207 break;
208 clearerr(fp);
209 queue = 1;
210 if (kq < 0 || kevent(kq, NULL, 0, &ke, 1, NULL) <= 0) {
211 queue = 0;
212 sleep(1);
213 } else if (ke.filter == EVFILT_READ) {
214 continue;
215 } else if ((ke.fflags & NOTE_TRUNCATE) == 0) {
216 /*
217 * File was renamed or deleted.
218 *
219 * Continue to look at it until a new file reappears
220 * with the same name.
221 * Fall back to the old algorithm for that.
222 */
223 close(kq);
224 kq = -1;
225 }
226
227 if (is_stdin || stat(fname, &nsb) != 0)
228 continue;
229 /* Reopen file if the inode changes or file was truncated */
230 if (nsb.st_ino != sbp->st_ino) {
231 warnx("%s has been replaced, reopening.", fname);
232 if ((fp = freopen(fname, "r", fp)) == NULL) {
233 ierr();
234 if (kq >= 0)
235 close(kq);
236 return;
237 }
238 (void)memcpy(sbp, &nsb, sizeof(nsb));
239 goto kq_retry;
240 } else if ((queue && (ke.fflags & NOTE_TRUNCATE)) ||
241 (!queue && nsb.st_size < sbp->st_size)) {
242 warnx("%s has been truncated, resetting.", fname);
243 fpurge(fp);
244 rewind(fp);
245 }
246 (void)memcpy(sbp, &nsb, sizeof(nsb));
247 }
248 if (kq >= 0)
249 close(kq);
250 }
251
252 /*
253 * rlines -- display the last offset lines of the file.
254 */
255 static int
rlines(FILE * fp,off_t off,struct stat * sbp)256 rlines(FILE *fp, off_t off, struct stat *sbp)
257 {
258 off_t pos;
259 int ch;
260
261 pos = sbp->st_size;
262 if (pos == 0)
263 return (0);
264
265 /*
266 * Position before char.
267 * Last char is special, ignore it whether newline or not.
268 */
269 pos -= 2;
270 ch = EOF;
271 for (; off > 0 && pos >= 0; pos--) {
272 /* A seek per char isn't a problem with a smart stdio */
273 if (fseeko(fp, pos, SEEK_SET) == -1) {
274 ierr();
275 return (1);
276 }
277 if ((ch = getc(fp)) == '\n')
278 off--;
279 else if (ch == EOF) {
280 if (ferror(fp)) {
281 ierr();
282 return (1);
283 }
284 break;
285 }
286 }
287 /* If we read until start of file, put back last read char */
288 if (pos < 0 && off > 0 && ch != EOF && ungetc(ch, fp) == EOF) {
289 ierr();
290 return (1);
291 }
292
293 while (!feof(fp) && (ch = getc(fp)) != EOF)
294 if (putchar(ch) == EOF)
295 oerr();
296 if (ferror(fp)) {
297 ierr();
298 return (1);
299 }
300
301 return (0);
302 }
303