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