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 * 4. 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 33 #include <sys/cdefs.h> 34 35 __FBSDID("$FreeBSD$"); 36 37 #ifndef lint 38 static const char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93"; 39 #endif 40 41 #include <sys/param.h> 42 #include <sys/mount.h> 43 #include <sys/types.h> 44 #include <sys/stat.h> 45 #include <sys/time.h> 46 #include <sys/mman.h> 47 #include <sys/event.h> 48 49 #include <err.h> 50 #include <errno.h> 51 #include <fcntl.h> 52 #include <limits.h> 53 #include <stdio.h> 54 #include <stdlib.h> 55 #include <string.h> 56 #include <unistd.h> 57 58 #include "extern.h" 59 60 static void rlines(FILE *, const char *fn, off_t, struct stat *); 61 static int show(file_info_t *); 62 static void set_events(file_info_t *files); 63 64 /* defines for inner loop actions */ 65 #define USE_SLEEP 0 66 #define USE_KQUEUE 1 67 #define ADD_EVENTS 2 68 69 static struct kevent *ev; 70 static int action = USE_SLEEP; 71 static int kq; 72 73 static const file_info_t *last; 74 75 /* 76 * forward -- display the file, from an offset, forward. 77 * 78 * There are eight separate cases for this -- regular and non-regular 79 * files, by bytes or lines and from the beginning or end of the file. 80 * 81 * FBYTES byte offset from the beginning of the file 82 * REG seek 83 * NOREG read, counting bytes 84 * 85 * FLINES line offset from the beginning of the file 86 * REG read, counting lines 87 * NOREG read, counting lines 88 * 89 * RBYTES byte offset from the end of the file 90 * REG seek 91 * NOREG cyclically read characters into a wrap-around buffer 92 * 93 * RLINES 94 * REG mmap the file and step back until reach the correct offset. 95 * NOREG cyclically read lines into a wrap-around array of buffers 96 */ 97 void 98 forward(FILE *fp, const char *fn, enum STYLE style, off_t off, struct stat *sbp) 99 { 100 int ch; 101 102 switch(style) { 103 case FBYTES: 104 if (off == 0) 105 break; 106 if (S_ISREG(sbp->st_mode)) { 107 if (sbp->st_size < off) 108 off = sbp->st_size; 109 if (fseeko(fp, off, SEEK_SET) == -1) { 110 ierr(fn); 111 return; 112 } 113 } else while (off--) 114 if ((ch = getc(fp)) == EOF) { 115 if (ferror(fp)) { 116 ierr(fn); 117 return; 118 } 119 break; 120 } 121 break; 122 case FLINES: 123 if (off == 0) 124 break; 125 for (;;) { 126 if ((ch = getc(fp)) == EOF) { 127 if (ferror(fp)) { 128 ierr(fn); 129 return; 130 } 131 break; 132 } 133 if (ch == '\n' && !--off) 134 break; 135 } 136 break; 137 case RBYTES: 138 if (S_ISREG(sbp->st_mode)) { 139 if (sbp->st_size >= off && 140 fseeko(fp, -off, SEEK_END) == -1) { 141 ierr(fn); 142 return; 143 } 144 } else if (off == 0) { 145 while (getc(fp) != EOF); 146 if (ferror(fp)) { 147 ierr(fn); 148 return; 149 } 150 } else 151 if (bytes(fp, fn, off)) 152 return; 153 break; 154 case RLINES: 155 if (S_ISREG(sbp->st_mode)) 156 if (!off) { 157 if (fseeko(fp, (off_t)0, SEEK_END) == -1) { 158 ierr(fn); 159 return; 160 } 161 } else 162 rlines(fp, fn, off, sbp); 163 else if (off == 0) { 164 while (getc(fp) != EOF); 165 if (ferror(fp)) { 166 ierr(fn); 167 return; 168 } 169 } else 170 if (lines(fp, fn, off)) 171 return; 172 break; 173 default: 174 break; 175 } 176 177 while ((ch = getc(fp)) != EOF) 178 if (putchar(ch) == EOF) 179 oerr(); 180 if (ferror(fp)) { 181 ierr(fn); 182 return; 183 } 184 (void)fflush(stdout); 185 } 186 187 /* 188 * rlines -- display the last offset lines of the file. 189 */ 190 static void 191 rlines(FILE *fp, const char *fn, off_t off, struct stat *sbp) 192 { 193 struct mapinfo map; 194 off_t curoff, size; 195 int i; 196 197 if (!(size = sbp->st_size)) 198 return; 199 map.start = NULL; 200 map.fd = fileno(fp); 201 map.mapoff = map.maxoff = size; 202 203 /* 204 * Last char is special, ignore whether newline or not. Note that 205 * size == 0 is dealt with above, and size == 1 sets curoff to -1. 206 */ 207 curoff = size - 2; 208 while (curoff >= 0) { 209 if (curoff < map.mapoff && maparound(&map, curoff) != 0) { 210 ierr(fn); 211 return; 212 } 213 for (i = curoff - map.mapoff; i >= 0; i--) 214 if (map.start[i] == '\n' && --off == 0) 215 break; 216 /* `i' is either the map offset of a '\n', or -1. */ 217 curoff = map.mapoff + i; 218 if (i >= 0) 219 break; 220 } 221 curoff++; 222 if (mapprint(&map, curoff, size - curoff) != 0) { 223 ierr(fn); 224 exit(1); 225 } 226 227 /* Set the file pointer to reflect the length displayed. */ 228 if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) { 229 ierr(fn); 230 return; 231 } 232 if (map.start != NULL && munmap(map.start, map.maplen)) { 233 ierr(fn); 234 return; 235 } 236 } 237 238 static int 239 show(file_info_t *file) 240 { 241 int ch; 242 243 while ((ch = getc(file->fp)) != EOF) { 244 if (last != file && no_files > 1) { 245 if (!qflag) 246 (void)printf("\n==> %s <==\n", file->file_name); 247 last = file; 248 } 249 if (putchar(ch) == EOF) 250 oerr(); 251 } 252 (void)fflush(stdout); 253 if (ferror(file->fp)) { 254 fclose(file->fp); 255 file->fp = NULL; 256 ierr(file->file_name); 257 return 0; 258 } 259 clearerr(file->fp); 260 return 1; 261 } 262 263 static void 264 set_events(file_info_t *files) 265 { 266 int i, n = 0; 267 file_info_t *file; 268 struct timespec ts; 269 struct statfs sf; 270 271 ts.tv_sec = 0; 272 ts.tv_nsec = 0; 273 274 action = USE_KQUEUE; 275 for (i = 0, file = files; i < no_files; i++, file++) { 276 if (! file->fp) 277 continue; 278 279 if (fstatfs(fileno(file->fp), &sf) == 0 && 280 (sf.f_flags & MNT_LOCAL) == 0) { 281 action = USE_SLEEP; 282 return; 283 } 284 285 if (Fflag && fileno(file->fp) != STDIN_FILENO) { 286 EV_SET(&ev[n], fileno(file->fp), EVFILT_VNODE, 287 EV_ADD | EV_ENABLE | EV_CLEAR, 288 NOTE_DELETE | NOTE_RENAME, 0, 0); 289 n++; 290 } 291 EV_SET(&ev[n], fileno(file->fp), EVFILT_READ, 292 EV_ADD | EV_ENABLE | EV_CLEAR, 0, 0, 0); 293 n++; 294 } 295 296 if (kevent(kq, ev, n, NULL, 0, &ts) < 0) { 297 action = USE_SLEEP; 298 } 299 } 300 301 /* 302 * follow -- display the file, from an offset, forward. 303 * 304 */ 305 void 306 follow(file_info_t *files, enum STYLE style, off_t off) 307 { 308 int active, ev_change, i, n = -1; 309 struct stat sb2; 310 file_info_t *file; 311 struct timespec ts; 312 313 /* Position each of the files */ 314 315 file = files; 316 active = 0; 317 n = 0; 318 for (i = 0; i < no_files; i++, file++) { 319 if (file->fp) { 320 active = 1; 321 n++; 322 if (no_files > 1 && !qflag) 323 (void)printf("\n==> %s <==\n", file->file_name); 324 forward(file->fp, file->file_name, style, off, &file->st); 325 if (Fflag && fileno(file->fp) != STDIN_FILENO) 326 n++; 327 } 328 } 329 if (!Fflag && !active) 330 return; 331 332 last = --file; 333 334 kq = kqueue(); 335 if (kq < 0) 336 err(1, "kqueue"); 337 ev = malloc(n * sizeof(struct kevent)); 338 if (! ev) 339 err(1, "Couldn't allocate memory for kevents."); 340 set_events(files); 341 342 for (;;) { 343 ev_change = 0; 344 if (Fflag) { 345 for (i = 0, file = files; i < no_files; i++, file++) { 346 if (!file->fp) { 347 file->fp = fopen(file->file_name, "r"); 348 if (file->fp != NULL && 349 fstat(fileno(file->fp), &file->st) 350 == -1) { 351 fclose(file->fp); 352 file->fp = NULL; 353 } 354 if (file->fp != NULL) 355 ev_change++; 356 continue; 357 } 358 if (fileno(file->fp) == STDIN_FILENO) 359 continue; 360 if (stat(file->file_name, &sb2) == -1) { 361 if (errno != ENOENT) 362 ierr(file->file_name); 363 show(file); 364 if (file->fp != NULL) { 365 fclose(file->fp); 366 file->fp = NULL; 367 } 368 ev_change++; 369 continue; 370 } 371 372 if (sb2.st_ino != file->st.st_ino || 373 sb2.st_dev != file->st.st_dev || 374 sb2.st_nlink == 0) { 375 show(file); 376 file->fp = freopen(file->file_name, "r", 377 file->fp); 378 if (file->fp != NULL) 379 memcpy(&file->st, &sb2, 380 sizeof(struct stat)); 381 else if (errno != ENOENT) 382 ierr(file->file_name); 383 ev_change++; 384 } 385 } 386 } 387 388 for (i = 0, file = files; i < no_files; i++, file++) 389 if (file->fp && !show(file)) 390 ev_change++; 391 392 if (ev_change) 393 set_events(files); 394 395 switch (action) { 396 case USE_KQUEUE: 397 ts.tv_sec = 1; 398 ts.tv_nsec = 0; 399 /* 400 * In the -F case we set a timeout to ensure that 401 * we re-stat the file at least once every second. 402 */ 403 n = kevent(kq, NULL, 0, ev, 1, Fflag ? &ts : NULL); 404 if (n < 0) 405 err(1, "kevent"); 406 if (n == 0) { 407 /* timeout */ 408 break; 409 } else if (ev->filter == EVFILT_READ && ev->data < 0) { 410 /* file shrank, reposition to end */ 411 if (lseek(ev->ident, (off_t)0, SEEK_END) == -1) { 412 ierr(file->file_name); 413 continue; 414 } 415 } 416 break; 417 418 case USE_SLEEP: 419 (void) usleep(250000); 420 break; 421 } 422 } 423 } 424