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 #ifndef lint 38 #if 0 39 static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93"; 40 #endif 41 static const char rcsid[] = 42 "$FreeBSD$"; 43 #endif /* not lint */ 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 <limits.h> 52 #include <fcntl.h> 53 #include <errno.h> 54 #include <unistd.h> 55 #include <stdio.h> 56 #include <stdlib.h> 57 #include <string.h> 58 #include <err.h> 59 #include "extern.h" 60 61 static void rlines __P((FILE *, long, struct stat *)); 62 63 /* defines for inner loop actions */ 64 #define USE_SLEEP 0 65 #define USE_KQUEUE 1 66 #define ADD_EVENTS 2 67 68 /* 69 * forward -- display the file, from an offset, forward. 70 * 71 * There are eight separate cases for this -- regular and non-regular 72 * files, by bytes or lines and from the beginning or end of the file. 73 * 74 * FBYTES byte offset from the beginning of the file 75 * REG seek 76 * NOREG read, counting bytes 77 * 78 * FLINES line offset from the beginning of the file 79 * REG read, counting lines 80 * NOREG read, counting lines 81 * 82 * RBYTES byte offset from the end of the file 83 * REG seek 84 * NOREG cyclically read characters into a wrap-around buffer 85 * 86 * RLINES 87 * REG mmap the file and step back until reach the correct offset. 88 * NOREG cyclically read lines into a wrap-around array of buffers 89 */ 90 void 91 forward(fp, style, off, sbp) 92 FILE *fp; 93 enum STYLE style; 94 long off; 95 struct stat *sbp; 96 { 97 int ch, kq = -1; 98 int action = USE_SLEEP; 99 struct kevent ev[2]; 100 struct stat sb2; 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 (fseek(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 fseek(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 (fseek(fp, 0L, 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 } 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 int n = 0; 198 struct timespec ts = { 0, 0 }; 199 200 if (Fflag && fileno(fp) != STDIN_FILENO) { 201 EV_SET(&ev[n], fileno(fp), EVFILT_VNODE, 202 EV_ADD | EV_ENABLE | EV_CLEAR, 203 NOTE_DELETE | NOTE_RENAME, 0, 0); 204 n++; 205 } 206 EV_SET(&ev[n], fileno(fp), EVFILT_READ, 207 EV_ADD | EV_ENABLE | EV_CLEAR, 0, 0, 0); 208 n++; 209 210 if (kevent(kq, ev, n, NULL, 0, &ts) < 0) { 211 close(kq); 212 kq = -1; 213 action = USE_SLEEP; 214 } else { 215 action = USE_KQUEUE; 216 } 217 break; 218 } 219 220 case USE_KQUEUE: 221 if (kevent(kq, NULL, 0, ev, 1, NULL) < 0) 222 err(1, "kevent"); 223 224 if (ev->filter == EVFILT_VNODE) { 225 /* file was rotated, wait until it reappears */ 226 action = USE_SLEEP; 227 } else if (ev->data < 0) { 228 /* file shrank, reposition to end */ 229 if (fseek(fp, 0L, SEEK_END) == -1) { 230 ierr(); 231 return; 232 } 233 } 234 break; 235 236 case USE_SLEEP: 237 (void) usleep(250000); 238 clearerr(fp); 239 240 if (Fflag && fileno(fp) != STDIN_FILENO && 241 stat(fname, &sb2) != -1) { 242 if (sb2.st_ino != sbp->st_ino || 243 sb2.st_dev != sbp->st_dev || 244 sb2.st_rdev != sbp->st_rdev || 245 sb2.st_nlink == 0) { 246 fp = freopen(fname, "r", fp); 247 if (fp == NULL) { 248 ierr(); 249 break; 250 } 251 *sbp = sb2; 252 if (kq != -1) 253 action = ADD_EVENTS; 254 } else if (kq != -1) { 255 action = USE_KQUEUE; 256 } 257 } 258 break; 259 } 260 } 261 } 262 263 /* 264 * rlines -- display the last offset lines of the file. 265 */ 266 static void 267 rlines(fp, off, sbp) 268 FILE *fp; 269 long off; 270 struct stat *sbp; 271 { 272 struct mapinfo map; 273 off_t curoff, size; 274 int i; 275 276 if (!(size = sbp->st_size)) 277 return; 278 map.start = NULL; 279 map.fd = fileno(fp); 280 map.mapoff = map.maxoff = size; 281 282 /* 283 * Last char is special, ignore whether newline or not. Note that 284 * size == 0 is dealt with above, and size == 1 sets curoff to -1. 285 */ 286 curoff = size - 2; 287 while (curoff >= 0) { 288 if (curoff < map.mapoff && maparound(&map, curoff) != 0) { 289 ierr(); 290 return; 291 } 292 for (i = curoff - map.mapoff; i >= 0; i--) 293 if (map.start[i] == '\n' && --off == 0) 294 break; 295 /* `i' is either the map offset of a '\n', or -1. */ 296 curoff = map.mapoff + i; 297 if (i >= 0) 298 break; 299 } 300 curoff++; 301 if (mapprint(&map, curoff, size - curoff) != 0) { 302 ierr(); 303 exit(1); 304 } 305 306 /* Set the file pointer to reflect the length displayed. */ 307 if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) { 308 ierr(); 309 return; 310 } 311 if (map.start != NULL && munmap(map.start, map.maplen)) { 312 ierr(); 313 return; 314 } 315 } 316