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 64 /* defines for inner loop actions */ 65 #define USE_SLEEP 0 66 #define USE_KQUEUE 1 67 #define ADD_EVENTS 2 68 69 /* 70 * forward -- display the file, from an offset, forward. 71 * 72 * There are eight separate cases for this -- regular and non-regular 73 * files, by bytes or lines and from the beginning or end of the file. 74 * 75 * FBYTES byte offset from the beginning of the file 76 * REG seek 77 * NOREG read, counting bytes 78 * 79 * FLINES line offset from the beginning of the file 80 * REG read, counting lines 81 * NOREG read, counting lines 82 * 83 * RBYTES byte offset from the end of the file 84 * REG seek 85 * NOREG cyclically read characters into a wrap-around buffer 86 * 87 * RLINES 88 * REG mmap the file and step back until reach the correct offset. 89 * NOREG cyclically read lines into a wrap-around array of buffers 90 */ 91 void 92 forward(FILE *fp, enum STYLE style, off_t off, struct stat *sbp) 93 { 94 int ch, n, kq = -1; 95 int action = USE_SLEEP; 96 struct kevent ev[2]; 97 struct stat sb2; 98 struct timespec ts; 99 100 switch(style) { 101 case FBYTES: 102 if (off == 0) 103 break; 104 if (S_ISREG(sbp->st_mode)) { 105 if (sbp->st_size < off) 106 off = sbp->st_size; 107 if (fseeko(fp, off, SEEK_SET) == -1) { 108 ierr(); 109 return; 110 } 111 } else while (off--) 112 if ((ch = getc(fp)) == EOF) { 113 if (ferror(fp)) { 114 ierr(); 115 return; 116 } 117 break; 118 } 119 break; 120 case FLINES: 121 if (off == 0) 122 break; 123 for (;;) { 124 if ((ch = getc(fp)) == EOF) { 125 if (ferror(fp)) { 126 ierr(); 127 return; 128 } 129 break; 130 } 131 if (ch == '\n' && !--off) 132 break; 133 } 134 break; 135 case RBYTES: 136 if (S_ISREG(sbp->st_mode)) { 137 if (sbp->st_size >= off && 138 fseeko(fp, -off, SEEK_END) == -1) { 139 ierr(); 140 return; 141 } 142 } else if (off == 0) { 143 while (getc(fp) != EOF); 144 if (ferror(fp)) { 145 ierr(); 146 return; 147 } 148 } else 149 if (bytes(fp, off)) 150 return; 151 break; 152 case RLINES: 153 if (S_ISREG(sbp->st_mode)) 154 if (!off) { 155 if (fseeko(fp, (off_t)0, SEEK_END) == -1) { 156 ierr(); 157 return; 158 } 159 } else 160 rlines(fp, off, sbp); 161 else if (off == 0) { 162 while (getc(fp) != EOF); 163 if (ferror(fp)) { 164 ierr(); 165 return; 166 } 167 } else 168 if (lines(fp, off)) 169 return; 170 break; 171 default: 172 break; 173 } 174 175 if (fflag) { 176 kq = kqueue(); 177 if (kq < 0) 178 err(1, "kqueue"); 179 action = ADD_EVENTS; 180 } 181 182 for (;;) { 183 while ((ch = getc(fp)) != EOF) 184 if (putchar(ch) == EOF) 185 oerr(); 186 if (ferror(fp)) { 187 ierr(); 188 return; 189 } 190 (void)fflush(stdout); 191 if (! fflag) 192 break; 193 clearerr(fp); 194 195 switch (action) { 196 case ADD_EVENTS: 197 n = 0; 198 ts.tv_sec = 0; 199 ts.tv_nsec = 0; 200 201 if (Fflag && fileno(fp) != STDIN_FILENO) { 202 EV_SET(&ev[n], fileno(fp), EVFILT_VNODE, 203 EV_ADD | EV_ENABLE | EV_CLEAR, 204 NOTE_DELETE | NOTE_RENAME, 0, 0); 205 n++; 206 } 207 EV_SET(&ev[n], fileno(fp), EVFILT_READ, 208 EV_ADD | EV_ENABLE | EV_CLEAR, 0, 0, 0); 209 n++; 210 211 if (kevent(kq, ev, n, NULL, 0, &ts) < 0) { 212 action = USE_SLEEP; 213 } else { 214 action = USE_KQUEUE; 215 } 216 break; 217 218 case USE_KQUEUE: 219 ts.tv_sec = 1; 220 ts.tv_nsec = 0; 221 /* 222 * In the -F case we set a timeout to ensure that 223 * we re-stat the file at least once every second. 224 */ 225 n = kevent(kq, NULL, 0, ev, 1, Fflag ? &ts : NULL); 226 if (n < 0) 227 err(1, "kevent"); 228 if (n == 0) { 229 /* timeout */ 230 break; 231 } else if (ev->filter == EVFILT_READ && ev->data < 0) { 232 /* file shrank, reposition to end */ 233 if (fseeko(fp, (off_t)0, SEEK_END) == -1) { 234 ierr(); 235 return; 236 } 237 } 238 break; 239 240 case USE_SLEEP: 241 (void) usleep(250000); 242 clearerr(fp); 243 break; 244 } 245 246 if (Fflag && fileno(fp) != STDIN_FILENO) { 247 while (stat(fname, &sb2) != 0) 248 /* file was rotated, wait until it reappears */ 249 (void)sleep(1); 250 if (sb2.st_ino != sbp->st_ino || 251 sb2.st_dev != sbp->st_dev || 252 sb2.st_nlink == 0) { 253 fp = freopen(fname, "r", fp); 254 if (fp == NULL) { 255 ierr(); 256 return; 257 } else { 258 *sbp = sb2; 259 action = ADD_EVENTS; 260 } 261 } 262 } 263 } 264 } 265 266 /* 267 * rlines -- display the last offset lines of the file. 268 */ 269 static void 270 rlines(fp, off, sbp) 271 FILE *fp; 272 off_t off; 273 struct stat *sbp; 274 { 275 struct mapinfo map; 276 off_t curoff, size; 277 int i; 278 279 if (!(size = sbp->st_size)) 280 return; 281 map.start = NULL; 282 map.fd = fileno(fp); 283 map.mapoff = map.maxoff = size; 284 285 /* 286 * Last char is special, ignore whether newline or not. Note that 287 * size == 0 is dealt with above, and size == 1 sets curoff to -1. 288 */ 289 curoff = size - 2; 290 while (curoff >= 0) { 291 if (curoff < map.mapoff && maparound(&map, curoff) != 0) { 292 ierr(); 293 return; 294 } 295 for (i = curoff - map.mapoff; i >= 0; i--) 296 if (map.start[i] == '\n' && --off == 0) 297 break; 298 /* `i' is either the map offset of a '\n', or -1. */ 299 curoff = map.mapoff + i; 300 if (i >= 0) 301 break; 302 } 303 curoff++; 304 if (mapprint(&map, curoff, size - curoff) != 0) { 305 ierr(); 306 exit(1); 307 } 308 309 /* Set the file pointer to reflect the length displayed. */ 310 if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) { 311 ierr(); 312 return; 313 } 314 if (map.start != NULL && munmap(map.start, map.maplen)) { 315 ierr(); 316 return; 317 } 318 } 319