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 /* 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, 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(); 111 return; 112 } 113 } else while (off--) 114 if ((ch = getc(fp)) == EOF) { 115 if (ferror(fp)) { 116 ierr(); 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(); 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(); 142 return; 143 } 144 } else if (off == 0) { 145 while (getc(fp) != EOF); 146 if (ferror(fp)) { 147 ierr(); 148 return; 149 } 150 } else 151 if (bytes(fp, 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(); 159 return; 160 } 161 } else 162 rlines(fp, off, sbp); 163 else if (off == 0) { 164 while (getc(fp) != EOF); 165 if (ferror(fp)) { 166 ierr(); 167 return; 168 } 169 } else 170 if (lines(fp, 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(); 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(fp, off, sbp) 192 FILE *fp; 193 off_t off; 194 struct stat *sbp; 195 { 196 struct mapinfo map; 197 off_t curoff, size; 198 int i; 199 200 if (!(size = sbp->st_size)) 201 return; 202 map.start = NULL; 203 map.fd = fileno(fp); 204 map.mapoff = map.maxoff = size; 205 206 /* 207 * Last char is special, ignore whether newline or not. Note that 208 * size == 0 is dealt with above, and size == 1 sets curoff to -1. 209 */ 210 curoff = size - 2; 211 while (curoff >= 0) { 212 if (curoff < map.mapoff && maparound(&map, curoff) != 0) { 213 ierr(); 214 return; 215 } 216 for (i = curoff - map.mapoff; i >= 0; i--) 217 if (map.start[i] == '\n' && --off == 0) 218 break; 219 /* `i' is either the map offset of a '\n', or -1. */ 220 curoff = map.mapoff + i; 221 if (i >= 0) 222 break; 223 } 224 curoff++; 225 if (mapprint(&map, curoff, size - curoff) != 0) { 226 ierr(); 227 exit(1); 228 } 229 230 /* Set the file pointer to reflect the length displayed. */ 231 if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) { 232 ierr(); 233 return; 234 } 235 if (map.start != NULL && munmap(map.start, map.maplen)) { 236 ierr(); 237 return; 238 } 239 } 240 241 /* 242 * follow -- display the file, from an offset, forward. 243 * 244 */ 245 246 static void 247 show(file_info_t *file) 248 { 249 int ch; 250 static file_info_t *last; 251 252 while ((ch = getc(file->fp)) != EOF) { 253 if (last != file && no_files > 1) { 254 (void)printf("\n==> %s <==\n", file->file_name); 255 last = file; 256 } 257 if (putchar(ch) == EOF) 258 oerr(); 259 } 260 (void)fflush(stdout); 261 if (ferror(file->fp)) { 262 file->fp = NULL; 263 ierr(); 264 } else 265 clearerr(file->fp); 266 } 267 268 static void 269 set_events(file_info_t *files) 270 { 271 int i, n = 0; 272 file_info_t *file; 273 struct timespec ts; 274 275 ts.tv_sec = 0; 276 ts.tv_nsec = 0; 277 278 action = USE_KQUEUE; 279 for (i = 0, file = files; i < no_files; i++, file++) { 280 if (! file->fp) 281 continue; 282 if (Fflag && fileno(file->fp) != STDIN_FILENO) { 283 EV_SET(&ev[n], fileno(file->fp), EVFILT_VNODE, 284 EV_ADD | EV_ENABLE | EV_CLEAR, 285 NOTE_DELETE | NOTE_RENAME, 0, 0); 286 n++; 287 } 288 EV_SET(&ev[n], fileno(file->fp), EVFILT_READ, 289 EV_ADD | EV_ENABLE | EV_CLEAR, 0, 0, 0); 290 n++; 291 } 292 293 if (kevent(kq, ev, n, NULL, 0, &ts) < 0) { 294 action = USE_SLEEP; 295 } 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 kq = kqueue(); 326 if (kq < 0) 327 err(1, "kqueue"); 328 ev = malloc(n * sizeof(struct kevent)); 329 if (! ev) 330 err(1, "Couldn't allocate memory for kevents."); 331 set_events(files); 332 333 for (;;) { 334 for (i = 0, file = files; i < no_files; i++, file++) { 335 if (! file->fp) 336 continue; 337 if (Fflag && file->fp && fileno(file->fp) != STDIN_FILENO) { 338 if (stat(file->file_name, &sb2) != 0) { 339 /* file was rotated, skip it until it reappears */ 340 continue; 341 } 342 if (sb2.st_ino != file->st.st_ino || 343 sb2.st_dev != file->st.st_dev || 344 sb2.st_nlink == 0) { 345 file->fp = freopen(file->file_name, "r", file->fp); 346 if (file->fp == NULL) { 347 ierr(); 348 continue; 349 } else { 350 memcpy(&file->st, &sb2, sizeof(struct stat)); 351 set_events(files); 352 } 353 } 354 } 355 show(file); 356 } 357 358 switch (action) { 359 case USE_KQUEUE: 360 ts.tv_sec = 1; 361 ts.tv_nsec = 0; 362 /* 363 * In the -F case we set a timeout to ensure that 364 * we re-stat the file at least once every second. 365 */ 366 n = kevent(kq, NULL, 0, ev, 1, Fflag ? &ts : NULL); 367 if (n < 0) 368 err(1, "kevent"); 369 if (n == 0) { 370 /* timeout */ 371 break; 372 } else if (ev->filter == EVFILT_READ && ev->data < 0) { 373 /* file shrank, reposition to end */ 374 if (lseek(ev->ident, (off_t)0, SEEK_END) == -1) { 375 ierr(); 376 continue; 377 } 378 } 379 break; 380 381 case USE_SLEEP: 382 (void) usleep(250000); 383 break; 384 } 385 } 386 } 387