1 /* $NetBSD: forward.c,v 1.16 1999/07/21 06:38:49 cgd 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 1.16 1999/07/21 06:38:49 cgd 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 __P((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(fp, style, off, sbp) 87 FILE *fp; 88 enum STYLE style; 89 long off; 90 struct stat *sbp; 91 { 92 int ch; 93 struct timeval second; 94 int dostat = 0; 95 struct stat statbuf; 96 off_t lastsize = 0; 97 dev_t lastdev; 98 ino_t lastino; 99 100 /* Keep track of file's previous incarnation. */ 101 lastdev = sbp->st_dev; 102 lastino = sbp->st_ino; 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 (fseek(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 fseek(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 } 156 break; 157 case RLINES: 158 if (S_ISREG(sbp->st_mode)) { 159 if (!off) { 160 if (fseek(fp, 0L, SEEK_END) == -1) { 161 ierr(); 162 return; 163 } 164 } else { 165 if (rlines(fp, off, sbp)) 166 return; 167 } 168 } else if (off == 0) { 169 while (getc(fp) != EOF); 170 if (ferror(fp)) { 171 ierr(); 172 return; 173 } 174 } else { 175 if (lines(fp, off)) 176 return; 177 } 178 break; 179 default: 180 break; 181 } 182 183 for (;;) { 184 while ((ch = getc(fp)) != EOF) { 185 if (putchar(ch) == EOF) 186 oerr(); 187 } 188 if (ferror(fp)) { 189 ierr(); 190 return; 191 } 192 (void)fflush(stdout); 193 if (!fflag) 194 break; 195 /* 196 * We pause for one second after displaying any data that has 197 * accumulated since we read the file. Since sleep(3) takes 198 * eight system calls, use select() instead. 199 */ 200 second.tv_sec = 1; 201 second.tv_usec = 0; 202 if (select(0, NULL, NULL, NULL, &second) == -1) 203 err(1, "select: %s", strerror(errno)); 204 clearerr(fp); 205 206 if (fflag == 1) 207 continue; 208 /* 209 * We restat the original filename every five seconds. If 210 * the size is ever smaller than the last time we read it, 211 * the file has probably been truncated; if the inode or 212 * or device number are different, it has been rotated. 213 * This causes us to close it, reopen it, and continue 214 * the tail -f. If stat returns an error (say, because 215 * the file has been removed), just continue with what 216 * we've got open now. 217 */ 218 if (dostat > 0) { 219 dostat -= 1; 220 } else { 221 dostat = 5; 222 if (stat(fname, &statbuf) == 0) { 223 if (statbuf.st_dev != lastdev || 224 statbuf.st_ino != lastino || 225 statbuf.st_size < lastsize) { 226 lastdev = statbuf.st_dev; 227 lastino = statbuf.st_ino; 228 lastsize = 0; 229 fclose(fp); 230 if ((fp = fopen(fname, "r")) == NULL) 231 err(1, "can't reopen %s: %s", 232 fname, strerror(errno)); 233 } else { 234 lastsize = statbuf.st_size; 235 } 236 } 237 } 238 } 239 } 240 241 /* 242 * rlines -- display the last offset lines of the file. 243 * 244 * Non-zero return means than a (non-fatal) error occurred. 245 */ 246 static int 247 rlines(fp, off, sbp) 248 FILE *fp; 249 long off; 250 struct stat *sbp; 251 { 252 off_t size; 253 char *p; 254 char *start; 255 256 if (!(size = sbp->st_size)) 257 return (0); 258 259 if (size > SIZE_T_MAX) { 260 err(0, "%s: %s", fname, strerror(EFBIG)); 261 return (1); 262 } 263 264 if ((start = mmap(NULL, (size_t)size, PROT_READ, 265 MAP_FILE|MAP_SHARED, fileno(fp), (off_t)0)) == (caddr_t)-1) { 266 err(0, "%s: %s", fname, strerror(EFBIG)); 267 return (1); 268 } 269 270 /* Last char is special, ignore whether newline or not. */ 271 for (p = start + size - 1; --size;) 272 if (*--p == '\n' && !--off) { 273 ++p; 274 break; 275 } 276 277 /* Set the file pointer to reflect the length displayed. */ 278 size = sbp->st_size - size; 279 WR(p, size); 280 if (fseek(fp, (long)sbp->st_size, SEEK_SET) == -1) { 281 ierr(); 282 return (1); 283 } 284 if (munmap(start, (size_t)sbp->st_size)) { 285 err(0, "%s: %s", fname, strerror(errno)); 286 return (1); 287 } 288 return (0); 289 } 290