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: src/usr.bin/tail/forward.c,v 1.11.6.7 2003/01/07 05:26:22 tjr Exp $"; 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 *, off_t, 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 off_t off; 95 struct stat *sbp; 96 { 97 int ch, n, kq = -1; 98 int action = USE_SLEEP; 99 struct kevent ev[2]; 100 struct stat sb2; 101 struct timespec ts; 102 103 switch(style) { 104 case FBYTES: 105 if (off == 0) 106 break; 107 if (S_ISREG(sbp->st_mode)) { 108 if (sbp->st_size < off) 109 off = sbp->st_size; 110 if (fseeko(fp, off, SEEK_SET) == -1) { 111 ierr(); 112 return; 113 } 114 } else while (off--) 115 if ((ch = getc(fp)) == EOF) { 116 if (ferror(fp)) { 117 ierr(); 118 return; 119 } 120 break; 121 } 122 break; 123 case FLINES: 124 if (off == 0) 125 break; 126 for (;;) { 127 if ((ch = getc(fp)) == EOF) { 128 if (ferror(fp)) { 129 ierr(); 130 return; 131 } 132 break; 133 } 134 if (ch == '\n' && !--off) 135 break; 136 } 137 break; 138 case RBYTES: 139 if (S_ISREG(sbp->st_mode)) { 140 if (sbp->st_size >= off && 141 fseeko(fp, -off, SEEK_END) == -1) { 142 ierr(); 143 return; 144 } 145 } else if (off == 0) { 146 while (getc(fp) != EOF); 147 if (ferror(fp)) { 148 ierr(); 149 return; 150 } 151 } else 152 if (bytes(fp, off)) 153 return; 154 break; 155 case RLINES: 156 if (S_ISREG(sbp->st_mode)) 157 if (!off) { 158 if (fseeko(fp, (off_t)0, SEEK_END) == -1) { 159 ierr(); 160 return; 161 } 162 } else 163 rlines(fp, off, sbp); 164 else if (off == 0) { 165 while (getc(fp) != EOF); 166 if (ferror(fp)) { 167 ierr(); 168 return; 169 } 170 } else 171 if (lines(fp, off)) 172 return; 173 break; 174 } 175 176 if (fflag) { 177 kq = kqueue(); 178 if (kq < 0) 179 err(1, "kqueue"); 180 action = ADD_EVENTS; 181 } 182 183 for (;;) { 184 while ((ch = getc(fp)) != EOF) 185 if (putchar(ch) == EOF) 186 oerr(); 187 if (ferror(fp)) { 188 ierr(); 189 return; 190 } 191 (void)fflush(stdout); 192 if (! fflag) 193 break; 194 clearerr(fp); 195 196 switch (action) { 197 case ADD_EVENTS: 198 n = 0; 199 ts.tv_sec = 0; 200 ts.tv_nsec = 0; 201 202 if (Fflag && fileno(fp) != STDIN_FILENO) { 203 EV_SET(&ev[n], fileno(fp), EVFILT_VNODE, 204 EV_ADD | EV_ENABLE | EV_CLEAR, 205 NOTE_DELETE | NOTE_RENAME, 0, 0); 206 n++; 207 } 208 EV_SET(&ev[n], fileno(fp), EVFILT_READ, 209 EV_ADD | EV_ENABLE | EV_CLEAR, 0, 0, 0); 210 n++; 211 212 if (kevent(kq, ev, n, NULL, 0, &ts) < 0) { 213 action = USE_SLEEP; 214 } else { 215 action = USE_KQUEUE; 216 } 217 break; 218 219 case USE_KQUEUE: 220 ts.tv_sec = 1; 221 ts.tv_nsec = 0; 222 /* 223 * In the -F case we set a timeout to ensure that 224 * we re-stat the file at least once every second. 225 */ 226 n = kevent(kq, NULL, 0, ev, 1, Fflag ? &ts : NULL); 227 if (n < 0) 228 err(1, "kevent"); 229 if (n == 0) { 230 /* timeout */ 231 break; 232 } else if (ev->filter == EVFILT_READ && ev->data < 0) { 233 /* file shrank, reposition to end */ 234 if (fseeko(fp, (off_t)0, SEEK_END) == -1) { 235 ierr(); 236 return; 237 } 238 } 239 break; 240 241 case USE_SLEEP: 242 (void) usleep(250000); 243 clearerr(fp); 244 break; 245 } 246 247 if (Fflag && fileno(fp) != STDIN_FILENO) { 248 while (stat(fname, &sb2) != 0) 249 /* file was rotated, wait until it reappears */ 250 (void)sleep(1); 251 if (sb2.st_ino != sbp->st_ino || 252 sb2.st_dev != sbp->st_dev || 253 sb2.st_rdev != sbp->st_rdev || 254 sb2.st_nlink == 0) { 255 fp = freopen(fname, "r", fp); 256 if (fp == NULL) { 257 ierr(); 258 return; 259 } else { 260 *sbp = sb2; 261 action = ADD_EVENTS; 262 } 263 } 264 } 265 } 266 } 267 268 /* 269 * rlines -- display the last offset lines of the file. 270 */ 271 static void 272 rlines(fp, off, sbp) 273 FILE *fp; 274 off_t off; 275 struct stat *sbp; 276 { 277 struct mapinfo map; 278 off_t curoff, size; 279 int i; 280 281 if (!(size = sbp->st_size)) 282 return; 283 map.start = NULL; 284 map.fd = fileno(fp); 285 map.mapoff = map.maxoff = size; 286 287 /* 288 * Last char is special, ignore whether newline or not. Note that 289 * size == 0 is dealt with above, and size == 1 sets curoff to -1. 290 */ 291 curoff = size - 2; 292 while (curoff >= 0) { 293 if (curoff < map.mapoff && maparound(&map, curoff) != 0) { 294 ierr(); 295 return; 296 } 297 for (i = curoff - map.mapoff; i >= 0; i--) 298 if (map.start[i] == '\n' && --off == 0) 299 break; 300 /* `i' is either the map offset of a '\n', or -1. */ 301 curoff = map.mapoff + i; 302 if (i >= 0) 303 break; 304 } 305 curoff++; 306 if (mapprint(&map, curoff, size - curoff) != 0) { 307 ierr(); 308 exit(1); 309 } 310 311 /* Set the file pointer to reflect the length displayed. */ 312 if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) { 313 ierr(); 314 return; 315 } 316 if (map.start != NULL && munmap(map.start, map.maplen)) { 317 ierr(); 318 return; 319 } 320 } 321