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 * $FreeBSD$ 37 */ 38 39 #ifndef lint 40 static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93"; 41 #endif /* not lint */ 42 43 #include <sys/types.h> 44 #include <sys/stat.h> 45 #include <sys/time.h> 46 #include <sys/mman.h> 47 #include <sys/event.h> 48 49 #include <limits.h> 50 #include <fcntl.h> 51 #include <errno.h> 52 #include <unistd.h> 53 #include <stdio.h> 54 #include <stdlib.h> 55 #include <string.h> 56 #include <err.h> 57 #include "extern.h" 58 59 static void rlines __P((FILE *, long, struct stat *)); 60 61 /* defines for inner loop actions */ 62 #define USE_SLEEP 0 63 #define USE_KQUEUE 1 64 #define ADD_EVENTS 2 65 66 /* 67 * forward -- display the file, from an offset, forward. 68 * 69 * There are eight separate cases for this -- regular and non-regular 70 * files, by bytes or lines and from the beginning or end of the file. 71 * 72 * FBYTES byte offset from the beginning of the file 73 * REG seek 74 * NOREG read, counting bytes 75 * 76 * FLINES line offset from the beginning of the file 77 * REG read, counting lines 78 * NOREG read, counting lines 79 * 80 * RBYTES byte offset from the end of the file 81 * REG seek 82 * NOREG cyclically read characters into a wrap-around buffer 83 * 84 * RLINES 85 * REG mmap the file and step back until reach the correct offset. 86 * NOREG cyclically read lines into a wrap-around array of buffers 87 */ 88 void 89 forward(fp, style, off, sbp) 90 FILE *fp; 91 enum STYLE style; 92 long off; 93 struct stat *sbp; 94 { 95 int ch, kq = -1; 96 int action = USE_SLEEP; 97 struct kevent ev[2]; 98 struct stat sb2; 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 (fseek(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 fseek(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 (fseek(fp, 0L, 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 } 172 173 if (fflag) { 174 kq = kqueue(); 175 if (kq < 0) 176 err(1, "kqueue"); 177 action = ADD_EVENTS; 178 } 179 180 for (;;) { 181 while ((ch = getc(fp)) != EOF) 182 if (putchar(ch) == EOF) 183 oerr(); 184 if (ferror(fp)) { 185 ierr(); 186 return; 187 } 188 (void)fflush(stdout); 189 if (! fflag) 190 break; 191 clearerr(fp); 192 193 switch (action) { 194 case ADD_EVENTS: { 195 int n = 0; 196 struct timespec ts = { 0, 0 }; 197 198 if (Fflag && fileno(fp) != STDIN_FILENO) { 199 ev[n].ident = fileno(fp); 200 ev[n].filter = EVFILT_VNODE; 201 ev[n].flags = EV_ADD | EV_ENABLE | EV_CLEAR; 202 ev[n].fflags = NOTE_DELETE | NOTE_RENAME; 203 n++; 204 } 205 ev[n].ident = fileno(fp); 206 ev[n].filter = EVFILT_READ; 207 ev[n].flags = EV_ADD | EV_ENABLE; 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 } 255 } 256 break; 257 } 258 } 259 } 260 261 /* 262 * rlines -- display the last offset lines of the file. 263 */ 264 static void 265 rlines(fp, off, sbp) 266 FILE *fp; 267 long off; 268 struct stat *sbp; 269 { 270 register off_t size; 271 register char *p; 272 char *start; 273 274 if (!(size = sbp->st_size)) 275 return; 276 277 if (size > SIZE_T_MAX) { 278 errno = EFBIG; 279 ierr(); 280 return; 281 } 282 283 if ((start = mmap(NULL, (size_t)size, 284 PROT_READ, MAP_SHARED, fileno(fp), (off_t)0)) == MAP_FAILED) { 285 ierr(); 286 return; 287 } 288 289 /* Last char is special, ignore whether newline or not. */ 290 for (p = start + size - 1; --size;) 291 if (*--p == '\n' && !--off) { 292 ++p; 293 break; 294 } 295 296 /* Set the file pointer to reflect the length displayed. */ 297 size = sbp->st_size - size; 298 WR(p, size); 299 if (fseek(fp, (long)sbp->st_size, SEEK_SET) == -1) { 300 ierr(); 301 return; 302 } 303 if (munmap(start, (size_t)sbp->st_size)) { 304 ierr(); 305 return; 306 } 307 } 308