1 /* $NetBSD: forward.c,v 1.22 2002/09/18 19:29:12 skrll Exp $ */ 2 3 /*- 4 * Copyright (c) 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Edward Sze-Tyan Wang. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #include <sys/cdefs.h> 40 #ifndef lint 41 #if 0 42 static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93"; 43 #endif 44 __RCSID("$NetBSD: forward.c,v 1.22 2002/09/18 19:29:12 skrll Exp $"); 45 #endif /* not lint */ 46 47 #include <sys/types.h> 48 #include <sys/stat.h> 49 #include <sys/time.h> 50 #include <sys/mman.h> 51 52 #include <limits.h> 53 #include <fcntl.h> 54 #include <errno.h> 55 #include <unistd.h> 56 #include <stdio.h> 57 #include <stdlib.h> 58 #include <string.h> 59 #include "extern.h" 60 61 static int rlines(FILE *, long, struct stat *); 62 63 /* 64 * forward -- display the file, from an offset, forward. 65 * 66 * There are eight separate cases for this -- regular and non-regular 67 * files, by bytes or lines and from the beginning or end of the file. 68 * 69 * FBYTES byte offset from the beginning of the file 70 * REG seek 71 * NOREG read, counting bytes 72 * 73 * FLINES line offset from the beginning of the file 74 * REG read, counting lines 75 * NOREG read, counting lines 76 * 77 * RBYTES byte offset from the end of the file 78 * REG seek 79 * NOREG cyclically read characters into a wrap-around buffer 80 * 81 * RLINES 82 * REG mmap the file and step back until reach the correct offset. 83 * NOREG cyclically read lines into a wrap-around array of buffers 84 */ 85 void 86 forward(FILE *fp, enum STYLE style, long int off, struct stat *sbp) 87 { 88 int ch; 89 struct timespec second; 90 int dostat = 0; 91 struct stat statbuf; 92 off_t lastsize = 0; 93 dev_t lastdev; 94 ino_t lastino; 95 96 /* Keep track of file's previous incarnation. */ 97 lastdev = sbp->st_dev; 98 lastino = sbp->st_ino; 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 } 152 break; 153 case RLINES: 154 if (S_ISREG(sbp->st_mode)) { 155 if (!off) { 156 if (fseek(fp, 0L, SEEK_END) == -1) { 157 ierr(); 158 return; 159 } 160 } else { 161 if (rlines(fp, off, sbp)) 162 return; 163 } 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 } 174 break; 175 default: 176 break; 177 } 178 179 for (;;) { 180 while ((ch = getc(fp)) != EOF) { 181 if (putchar(ch) == EOF) 182 oerr(); 183 } 184 if (ferror(fp)) { 185 ierr(); 186 return; 187 } 188 (void)fflush(stdout); 189 if (!fflag) 190 break; 191 /* 192 * We pause for one second after displaying any data that has 193 * accumulated since we read the file. 194 */ 195 second.tv_sec = 1; 196 second.tv_nsec = 0; 197 if (nanosleep(&second, NULL) == -1) 198 err(1, "nanosleep: %s", strerror(errno)); 199 clearerr(fp); 200 201 if (fflag == 1) 202 continue; 203 /* 204 * We restat the original filename every five seconds. If 205 * the size is ever smaller than the last time we read it, 206 * the file has probably been truncated; if the inode or 207 * or device number are different, it has been rotated. 208 * This causes us to close it, reopen it, and continue 209 * the tail -f. If stat returns an error (say, because 210 * the file has been removed), just continue with what 211 * we've got open now. 212 */ 213 if (dostat > 0) { 214 dostat -= 1; 215 } else { 216 dostat = 5; 217 if (stat(fname, &statbuf) == 0) { 218 if (statbuf.st_dev != lastdev || 219 statbuf.st_ino != lastino || 220 statbuf.st_size < lastsize) { 221 lastdev = statbuf.st_dev; 222 lastino = statbuf.st_ino; 223 lastsize = 0; 224 fclose(fp); 225 if ((fp = fopen(fname, "r")) == NULL) 226 err(1, "can't reopen %s: %s", 227 fname, strerror(errno)); 228 } else { 229 lastsize = statbuf.st_size; 230 } 231 } 232 } 233 } 234 } 235 236 /* 237 * rlines -- display the last offset lines of the file. 238 * 239 * Non-zero return means than a (non-fatal) error occurred. 240 */ 241 static int 242 rlines(FILE *fp, long int off, struct stat *sbp) 243 { 244 off_t file_size; 245 off_t file_remaining; 246 char *p; 247 char *start; 248 off_t mmap_size; 249 off_t mmap_offset; 250 off_t mmap_remaining; 251 252 #define MMAP_MAXSIZE (10 * 1024 * 1024) 253 254 if (!(file_size = sbp->st_size)) 255 return (0); 256 file_remaining = file_size; 257 258 if (file_remaining > MMAP_MAXSIZE) { 259 mmap_size = MMAP_MAXSIZE; 260 mmap_offset = file_remaining - MMAP_MAXSIZE; 261 } else { 262 mmap_size = file_remaining; 263 mmap_offset = 0; 264 } 265 266 while (off) { 267 start = mmap(NULL, (size_t)mmap_size, PROT_READ, 268 MAP_FILE|MAP_SHARED, fileno(fp), mmap_offset); 269 if (start == MAP_FAILED) { 270 err(0, "%s: %s", fname, strerror(EFBIG)); 271 return (1); 272 } 273 274 mmap_remaining = mmap_size; 275 /* Last char is special, ignore whether newline or not. */ 276 for (p = start + mmap_remaining - 1 ; --mmap_remaining ; ) 277 if (*--p == '\n' && !--off) { 278 ++p; 279 break; 280 } 281 282 file_remaining -= mmap_size - mmap_remaining; 283 284 if (off == 0) 285 break; 286 287 if (file_remaining == 0) 288 break; 289 290 if (munmap(start, mmap_size)) { 291 err(0, "%s: %s", fname, strerror(errno)); 292 return (1); 293 } 294 295 if (mmap_offset >= MMAP_MAXSIZE) { 296 mmap_offset -= MMAP_MAXSIZE; 297 } else { 298 mmap_offset = 0; 299 mmap_size = file_remaining; 300 } 301 } 302 303 /* 304 * Output the (perhaps partial) data in this mmap'd block. 305 */ 306 WR(p, mmap_size - mmap_remaining); 307 file_remaining += mmap_size - mmap_remaining; 308 if (munmap(start, mmap_size)) { 309 err(0, "%s: %s", fname, strerror(errno)); 310 return (1); 311 } 312 313 /* 314 * Set the file pointer to reflect the length displayed. 315 * This will cause the caller to redisplay the data if/when 316 * needed. 317 */ 318 if (fseeko(fp, file_remaining, SEEK_SET) == -1) { 319 ierr(); 320 return (1); 321 } 322 return (0); 323 } 324