forward.c revision 118900
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: head/usr.bin/tail/forward.c 118900 2003-08-14 11:02:03Z dg $"); 40 41#ifndef lint 42static 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 62static 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 */ 91void 92forward(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 break; 177 } 178 179 if (fflag) { 180 kq = kqueue(); 181 if (kq < 0) 182 err(1, "kqueue"); 183 action = ADD_EVENTS; 184 } 185 186 for (;;) { 187 while ((ch = getc(fp)) != EOF) 188 if (putchar(ch) == EOF) 189 oerr(); 190 if (ferror(fp)) { 191 ierr(); 192 return; 193 } 194 (void)fflush(stdout); 195 if (! fflag) 196 break; 197 clearerr(fp); 198 199 switch (action) { 200 case ADD_EVENTS: 201 n = 0; 202 ts.tv_sec = 0; 203 ts.tv_nsec = 0; 204 205 if (Fflag && fileno(fp) != STDIN_FILENO) { 206 EV_SET(&ev[n], fileno(fp), EVFILT_VNODE, 207 EV_ADD | EV_ENABLE | EV_CLEAR, 208 NOTE_DELETE | NOTE_RENAME, 0, 0); 209 n++; 210 } 211 EV_SET(&ev[n], fileno(fp), EVFILT_READ, 212 EV_ADD | EV_ENABLE | EV_CLEAR, 0, 0, 0); 213 n++; 214 215 if (kevent(kq, ev, n, NULL, 0, &ts) < 0) { 216 action = USE_SLEEP; 217 } else { 218 action = USE_KQUEUE; 219 } 220 break; 221 222 case USE_KQUEUE: 223 ts.tv_sec = 1; 224 ts.tv_nsec = 0; 225 /* 226 * In the -F case we set a timeout to ensure that 227 * we re-stat the file at least once every second. 228 */ 229 n = kevent(kq, NULL, 0, ev, 1, Fflag ? &ts : NULL); 230 if (n < 0) 231 err(1, "kevent"); 232 if (n == 0) { 233 /* timeout */ 234 break; 235 } else if (ev->filter == EVFILT_READ && ev->data < 0) { 236 /* file shrank, reposition to end */ 237 if (fseeko(fp, (off_t)0, SEEK_END) == -1) { 238 ierr(); 239 return; 240 } 241 } 242 break; 243 244 case USE_SLEEP: 245 (void) usleep(250000); 246 clearerr(fp); 247 break; 248 } 249 250 if (Fflag && fileno(fp) != STDIN_FILENO) { 251 while (stat(fname, &sb2) != 0) 252 /* file was rotated, wait until it reappears */ 253 (void)sleep(1); 254 if (sb2.st_ino != sbp->st_ino || 255 sb2.st_dev != sbp->st_dev || 256 sb2.st_nlink == 0) { 257 fp = freopen(fname, "r", fp); 258 if (fp == NULL) { 259 ierr(); 260 return; 261 } else { 262 *sbp = sb2; 263 action = ADD_EVENTS; 264 } 265 } 266 } 267 } 268} 269 270/* 271 * rlines -- display the last offset lines of the file. 272 */ 273static void 274rlines(fp, off, sbp) 275 FILE *fp; 276 off_t off; 277 struct stat *sbp; 278{ 279 struct mapinfo map; 280 off_t curoff, size; 281 int i; 282 283 if (!(size = sbp->st_size)) 284 return; 285 map.start = NULL; 286 map.fd = fileno(fp); 287 map.mapoff = map.maxoff = size; 288 289 /* 290 * Last char is special, ignore whether newline or not. Note that 291 * size == 0 is dealt with above, and size == 1 sets curoff to -1. 292 */ 293 curoff = size - 2; 294 while (curoff >= 0) { 295 if (curoff < map.mapoff && maparound(&map, curoff) != 0) { 296 ierr(); 297 return; 298 } 299 for (i = curoff - map.mapoff; i >= 0; i--) 300 if (map.start[i] == '\n' && --off == 0) 301 break; 302 /* `i' is either the map offset of a '\n', or -1. */ 303 curoff = map.mapoff + i; 304 if (i >= 0) 305 break; 306 } 307 curoff++; 308 if (mapprint(&map, curoff, size - curoff) != 0) { 309 ierr(); 310 exit(1); 311 } 312 313 /* Set the file pointer to reflect the length displayed. */ 314 if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) { 315 ierr(); 316 return; 317 } 318 if (map.start != NULL && munmap(map.start, map.maplen)) { 319 ierr(); 320 return; 321 } 322} 323