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 __P((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(fp, style, off, sbp) 93 FILE *fp; 94 enum STYLE style; 95 off_t off; 96 struct stat *sbp; 97 { 98 int ch, n, kq = -1; 99 int action = USE_SLEEP; 100 struct kevent ev[2]; 101 struct stat sb2; 102 struct timespec ts; 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 } 177 178 if (fflag) { 179 kq = kqueue(); 180 if (kq < 0) 181 err(1, "kqueue"); 182 action = ADD_EVENTS; 183 } 184 185 for (;;) { 186 while ((ch = getc(fp)) != EOF) 187 if (putchar(ch) == EOF) 188 oerr(); 189 if (ferror(fp)) { 190 ierr(); 191 return; 192 } 193 (void)fflush(stdout); 194 if (! fflag) 195 break; 196 clearerr(fp); 197 198 switch (action) { 199 case ADD_EVENTS: 200 n = 0; 201 ts.tv_sec = 0; 202 ts.tv_nsec = 0; 203 204 if (Fflag && fileno(fp) != STDIN_FILENO) { 205 EV_SET(&ev[n], fileno(fp), EVFILT_VNODE, 206 EV_ADD | EV_ENABLE | EV_CLEAR, 207 NOTE_DELETE | NOTE_RENAME, 0, 0); 208 n++; 209 } 210 EV_SET(&ev[n], fileno(fp), EVFILT_READ, 211 EV_ADD | EV_ENABLE | EV_CLEAR, 0, 0, 0); 212 n++; 213 214 if (kevent(kq, ev, n, NULL, 0, &ts) < 0) { 215 action = USE_SLEEP; 216 } else { 217 action = USE_KQUEUE; 218 } 219 break; 220 221 case USE_KQUEUE: 222 ts.tv_sec = 1; 223 ts.tv_nsec = 0; 224 /* 225 * In the -F case we set a timeout to ensure that 226 * we re-stat the file at least once every second. 227 */ 228 n = kevent(kq, NULL, 0, ev, 1, Fflag ? &ts : NULL); 229 if (n < 0) 230 err(1, "kevent"); 231 if (n == 0) { 232 /* timeout */ 233 break; 234 } else if (ev->filter == EVFILT_READ && ev->data < 0) { 235 /* file shrank, reposition to end */ 236 if (fseeko(fp, (off_t)0, SEEK_END) == -1) { 237 ierr(); 238 return; 239 } 240 } 241 break; 242 243 case USE_SLEEP: 244 (void) usleep(250000); 245 clearerr(fp); 246 break; 247 } 248 249 if (Fflag && fileno(fp) != STDIN_FILENO) { 250 while (stat(fname, &sb2) != 0) 251 /* file was rotated, wait until it reappears */ 252 (void)sleep(1); 253 if (sb2.st_ino != sbp->st_ino || 254 sb2.st_dev != sbp->st_dev || 255 sb2.st_rdev != sbp->st_rdev || 256 sb2.st_nlink == 0) { 257 fp = freopen(fname, "r", fp); 258 if (fp == NULL) { 259 ierr(); 260 } else { 261 *sbp = sb2; 262 action = ADD_EVENTS; 263 } 264 } 265 } 266 } 267 } 268 269 /* 270 * rlines -- display the last offset lines of the file. 271 */ 272 static void 273 rlines(fp, off, sbp) 274 FILE *fp; 275 off_t off; 276 struct stat *sbp; 277 { 278 struct mapinfo map; 279 off_t curoff, size; 280 int i; 281 282 if (!(size = sbp->st_size)) 283 return; 284 map.start = NULL; 285 map.fd = fileno(fp); 286 map.mapoff = map.maxoff = size; 287 288 /* 289 * Last char is special, ignore whether newline or not. Note that 290 * size == 0 is dealt with above, and size == 1 sets curoff to -1. 291 */ 292 curoff = size - 2; 293 while (curoff >= 0) { 294 if (curoff < map.mapoff && maparound(&map, curoff) != 0) { 295 ierr(); 296 return; 297 } 298 for (i = curoff - map.mapoff; i >= 0; i--) 299 if (map.start[i] == '\n' && --off == 0) 300 break; 301 /* `i' is either the map offset of a '\n', or -1. */ 302 curoff = map.mapoff + i; 303 if (i >= 0) 304 break; 305 } 306 curoff++; 307 if (mapprint(&map, curoff, size - curoff) != 0) { 308 ierr(); 309 exit(1); 310 } 311 312 /* Set the file pointer to reflect the length displayed. */ 313 if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) { 314 ierr(); 315 return; 316 } 317 if (map.start != NULL && munmap(map.start, map.maplen)) { 318 ierr(); 319 return; 320 } 321 } 322