usr.bin/tail/forward.c

   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. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * @(#)forward.c        8.1 (Berkeley) 6/6/93
  33  * $FreeBSD: src/usr.bin/tail/forward.c,v 1.11.6.7 2003/01/07 05:26:22 tjr Exp $
  34  */
  35
  36 #include <sys/types.h>
  37 #include <sys/stat.h>
  38 #include <sys/time.h>
  39 #include <sys/mman.h>
  40 #ifndef BOOTSTRAPPING
  41 #include <sys/event.h>
  42 #endif
  43
  44 #include <limits.h>
  45 #include <fcntl.h>
  46 #include <errno.h>
  47 #include <unistd.h>
  48 #include <stdio.h>
  49 #include <stdlib.h>
  50 #include <string.h>
  51 #include <err.h>
  52 #include "extern.h"
  53
  54 static void rlines(FILE *, off_t, struct stat *);
  55
  56 /* defines for inner loop actions */
  57 #define USE_SLEEP       0
  58 #ifndef BOOTSTRAPPING
  59 #define USE_KQUEUE      1
  60 #define ADD_EVENTS      2
  61
  62 struct kevent *ev;
  63 #endif
  64 int action = USE_SLEEP;
  65 int kq;
  66
  67 /*
  68  * forward -- display the file, from an offset, forward.
  69  *
  70  * There are eight separate cases for this -- regular and non-regular
  71  * files, by bytes or lines and from the beginning or end of the file.
  72  *
  73  * FBYTES       byte offset from the beginning of the file
  74  *      REG     seek
  75  *      NOREG   read, counting bytes
  76  *
  77  * FLINES       line offset from the beginning of the file
  78  *      REG     read, counting lines
  79  *      NOREG   read, counting lines
  80  *
  81  * RBYTES       byte offset from the end of the file
  82  *      REG     seek
  83  *      NOREG   cyclically read characters into a wrap-around buffer
  84  *
  85  * RLINES
  86  *      REG     mmap the file and step back until reach the correct offset.
  87  *      NOREG   cyclically read lines into a wrap-around array of buffers
  88  */
  89 void
  90 forward(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
  91 {
  92         int ch;
  93
  94         switch(style) {
  95         case FBYTES:
  96                 if (off == 0)
  97                         break;
  98                 if (S_ISREG(sbp->st_mode)) {
  99                         if (sbp->st_size < off)
 100                                 off = sbp->st_size;
 101                         if (fseeko(fp, off, SEEK_SET) == -1) {
 102                                 ierr();
 103                                 return;
 104                         }
 105                 } else while (off--)
 106                         if ((ch = getc(fp)) == EOF) {
 107                                 if (ferror(fp)) {
 108                                         ierr();
 109                                         return;
 110                                 }
 111                                 break;
 112                         }
 113                 break;
 114         case FLINES:
 115                 if (off == 0)
 116                         break;
 117                 for (;;) {
 118                         if ((ch = getc(fp)) == EOF) {
 119                                 if (ferror(fp)) {
 120                                         ierr();
 121                                         return;
 122                                 }
 123                                 break;
 124                         }
 125                         if (ch == '\n' && !--off)
 126                                 break;
 127                 }
 128                 break;
 129         case RBYTES:
 130                 if (S_ISREG(sbp->st_mode)) {
 131                         if (sbp->st_size >= off &&
 132                             fseeko(fp, -off, SEEK_END) == -1) {
 133                                 ierr();
 134                                 return;
 135                         }
 136                 } else if (off == 0) {
 137                         while (getc(fp) != EOF);
 138                         if (ferror(fp)) {
 139                                 ierr();
 140                                 return;
 141                         }
 142                 } else
 143                         if (display_bytes(fp, off))
 144                                 return;
 145                 break;
 146         case RLINES:
 147                 if (S_ISREG(sbp->st_mode) && sbp->st_size != 0)
 148                         if (!off) {
 149                                 if (fseeko(fp, (off_t)0, SEEK_END) == -1) {
 150                                         ierr();
 151                                         return;
 152                                 }
 153                         } else
 154                                 rlines(fp, off, sbp);
 155                 else if (off == 0) {
 156                         while (getc(fp) != EOF);
 157                         if (ferror(fp)) {
 158                                 ierr();
 159                                 return;
 160                         }
 161                 } else
 162                         if (display_lines(fp, off))
 163                                 return;
 164                 break;
 165         case REVERSE:
 166                 errx(1, "internal error: forward style cannot be REVERSE");
 167                 /* NOTREACHED */
 168         }
 169
 170         while ((ch = getc(fp)) != EOF) {
 171                 if (putchar(ch) == EOF)
 172                         oerr();
 173         }
 174         if (ferror(fp)) {
 175                 ierr();
 176                 return;
 177         }
 178         fflush(stdout);
 179 }
 180
 181 /*
 182  * rlines -- display the last offset lines of the file.
 183  */
 184 static void
 185 rlines(FILE *fp, off_t off, struct stat *sbp)
 186 {
 187         struct mapinfo map;
 188         off_t curoff, size;
 189         int i;
 190
 191         if (!(size = sbp->st_size))
 192                 return;
 193         map.start = NULL;
 194         map.fd = fileno(fp);
 195         map.mapoff = map.maxoff = size;
 196
 197         /*
 198          * Last char is special, ignore whether newline or not. Note that
 199          * size == 0 is dealt with above, and size == 1 sets curoff to -1.
 200          */
 201         curoff = size - 2;
 202         while (curoff >= 0) {
 203                 if (curoff < map.mapoff && maparound(&map, curoff) != 0) {
 204                         ierr();
 205                         return;
 206                 }
 207                 for (i = curoff - map.mapoff; i >= 0; i--)
 208                         if (map.start[i] == '\n' && --off == 0)
 209                                 break;
 210                 /* `i' is either the map offset of a '\n', or -1. */
 211                 curoff = map.mapoff + i;
 212                 if (i >= 0)
 213                         break;
 214         }
 215         curoff++;
 216         if (mapprint(&map, curoff, size - curoff) != 0) {
 217                 ierr();
 218                 exit(1);
 219         }
 220
 221         /* Set the file pointer to reflect the length displayed. */
 222         if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) {
 223                 ierr();
 224                 return;
 225         }
 226         if (map.start != NULL && munmap(map.start, map.maplen)) {
 227                 ierr();
 228                 return;
 229         }
 230 }
 231
 232 /*
 233  * follow -- display the file, from an offset, forward.
 234  */
 235 #ifndef BOOTSTRAPPING
 236 static void
 237 show(file_info_t *file, int at_index)
 238 {
 239         int ch, first;
 240
 241         first = 1;
 242         while ((ch = getc(file->fp)) != EOF) {
 243                 if (first && no_files > 1) {
 244                         showfilename(at_index, file->file_name);
 245                         first = 0;
 246                 }
 247                 if (putchar(ch) == EOF)
 248                         oerr();
 249         }
 250         fflush(stdout);
 251         if (ferror(file->fp)) {
 252                 file->fp = NULL;
 253                 ierr();
 254         } else {
 255                 clearerr(file->fp);
 256         }
 257 }
 258 #endif
 259
 260 void
 261 showfilename(int at_index, const char *filename)
 262 {
 263         static int last_index = -1;
 264         static int continuing = 0;
 265
 266         if (last_index == at_index)
 267                 return;
 268         if (!qflag) {
 269                 if (continuing)
 270                         printf("\n");
 271                 printf("==> %s <==\n", filename);
 272         }
 273         continuing = 1;
 274         last_index = at_index;
 275 }
 276
 277 #ifndef BOOTSTRAPPING
 278 static void
 279 set_events(file_info_t *files)
 280 {
 281         int i, n;
 282         file_info_t *file;
 283         struct timespec ts;
 284
 285         ts.tv_sec = 0;
 286         ts.tv_nsec = 0;
 287
 288         n = 0;
 289         action = USE_KQUEUE;
 290         for (i = 0, file = files; i < no_files; i++, file++) {
 291                 if (file->fp == NULL)
 292                         continue;
 293                 if (Fflag && fileno(file->fp) != STDIN_FILENO) {
 294                         EV_SET(&ev[n], fileno(file->fp), EVFILT_VNODE,
 295                                EV_ADD | EV_ENABLE | EV_CLEAR,
 296                                NOTE_DELETE | NOTE_RENAME, 0, 0);
 297                         n++;
 298                 }
 299                 EV_SET(&ev[n], fileno(file->fp), EVFILT_READ,
 300                        EV_ADD | EV_ENABLE | EV_CLEAR, 0, 0, 0);
 301                 n++;
 302         }
 303
 304         if (kevent(kq, ev, n, NULL, 0, &ts) < 0)
 305                 action = USE_SLEEP;
 306 }
 307
 308 void
 309 follow(file_info_t *files, enum STYLE style, off_t off)
 310 {
 311         int active, i, n;
 312         file_info_t *file;
 313         struct stat sb2;
 314         struct timespec ts;
 315
 316         /* Position each of the files */
 317         file = files;
 318         active = 0;
 319         n = 0;
 320         for (i = 0; i < no_files; i++, file++) {
 321                 if (file->fp) {
 322                         active = 1;
 323                         n++;
 324                         if (vflag || no_files > 1)
 325                                 showfilename(i, file->file_name);
 326                         forward(file->fp, style, off, &file->st);
 327                         if (Fflag && fileno(file->fp) != STDIN_FILENO)
 328                                 n++;
 329                 }
 330         }
 331
 332         if (!active)
 333                 return;
 334
 335         kq = kqueue();
 336         if (kq == -1)
 337                 err(1, "kqueue");
 338         ev = malloc(n * sizeof(struct kevent));
 339         if (ev == NULL)
 340                 err(1, "Couldn't allocate memory for kevents.");
 341         set_events(files);
 342
 343         for (;;) {
 344                 for (i = 0, file = files; i < no_files; i++, file++) {
 345                         if (file->fp == NULL)
 346                                 continue;
 347                         if (Fflag && fileno(file->fp) != STDIN_FILENO) {
 348                                 if (stat(file->file_name, &sb2) == -1) {
 349                                         /*
 350                                          * file was rotated, skip it until it
 351                                          * reappears.
 352                                          */
 353                                         continue;
 354                                 }
 355                                 if (sb2.st_ino != file->st.st_ino ||
 356                                     sb2.st_dev != file->st.st_dev ||
 357                                     sb2.st_nlink == 0) {
 358                                         file->fp = freopen(file->file_name, "r",
 359                                                            file->fp);
 360                                         if (file->fp == NULL) {
 361                                                 ierr();
 362                                                 continue;
 363                                         } else {
 364                                                 memcpy(&file->st, &sb2,
 365                                                        sizeof(struct stat));
 366                                                 set_events(files);
 367                                         }
 368                                 }
 369                         }
 370                         show(file, i);
 371                 }
 372
 373                 switch (action) {
 374                 case USE_KQUEUE:
 375                         ts.tv_sec = 1;
 376                         ts.tv_nsec = 0;
 377                         /*
 378                          * In the -F case, we set a timeout to ensure that
 379                          * we re-stat the file at least once every second.
 380                          */
 381                         n = kevent(kq, NULL, 0, ev, 1, Fflag ? &ts : NULL);
 382                         if (n == -1)
 383                                 err(1, "kevent");
 384                         if (n == 0) {
 385                                 /* timeout */
 386                                 break;
 387                         } else if (ev->filter == EVFILT_READ && ev->data < 0) {
 388                                 /* file shrank, reposition to end */
 389                                 if (lseek(ev->ident, 0, SEEK_END) == -1) {
 390                                         ierr();
 391                                         continue;
 392                                 }
 393                         }
 394                         break;
 395
 396                 case USE_SLEEP:
 397                         usleep(250000);
 398                         break;
 399                 }
 400         }
 401 }
 402 #endif