usr.bin/tail/forward.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-3-Clause
   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. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34
  35 #include <sys/cdefs.h>
  36
  37 __FBSDID("$FreeBSD$");
  38
  39 #ifndef lint
  40 static const char sccsid[] = "@(#)forward.c     8.1 (Berkeley) 6/6/93";
  41 #endif
  42
  43 #include <sys/param.h>
  44 #include <sys/mount.h>
  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
  62 static void rlines(FILE *, const char *fn, off_t, struct stat *);
  63 static int show(file_info_t *);
  64 static void set_events(file_info_t *files);
  65
  66 /* defines for inner loop actions */
  67 #define USE_SLEEP       0
  68 #define USE_KQUEUE      1
  69 #define ADD_EVENTS      2
  70
  71 static struct kevent *ev;
  72 static int action = USE_SLEEP;
  73 static int kq;
  74
  75 static const file_info_t *last;
  76
  77 /*
  78  * forward -- display the file, from an offset, forward.
  79  *
  80  * There are eight separate cases for this -- regular and non-regular
  81  * files, by bytes or lines and from the beginning or end of the file.
  82  *
  83  * FBYTES       byte offset from the beginning of the file
  84  *      REG     seek
  85  *      NOREG   read, counting bytes
  86  *
  87  * FLINES       line offset from the beginning of the file
  88  *      REG     read, counting lines
  89  *      NOREG   read, counting lines
  90  *
  91  * RBYTES       byte offset from the end of the file
  92  *      REG     seek
  93  *      NOREG   cyclically read characters into a wrap-around buffer
  94  *
  95  * RLINES
  96  *      REG     mmap the file and step back until reach the correct offset.
  97  *      NOREG   cyclically read lines into a wrap-around array of buffers
  98  */
  99 void
 100 forward(FILE *fp, const char *fn, enum STYLE style, off_t off, struct stat *sbp)
 101 {
 102         int ch;
 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(fn);
 113                                 return;
 114                         }
 115                 } else while (off--)
 116                         if ((ch = getc(fp)) == EOF) {
 117                                 if (ferror(fp)) {
 118                                         ierr(fn);
 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(fn);
 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(fn);
 144                                 return;
 145                         }
 146                 } else if (off == 0) {
 147                         while (getc(fp) != EOF);
 148                         if (ferror(fp)) {
 149                                 ierr(fn);
 150                                 return;
 151                         }
 152                 } else
 153                         if (bytes(fp, fn, 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(fn);
 161                                         return;
 162                                 }
 163                         } else
 164                                 rlines(fp, fn, off, sbp);
 165                 else if (off == 0) {
 166                         while (getc(fp) != EOF);
 167                         if (ferror(fp)) {
 168                                 ierr(fn);
 169                                 return;
 170                         }
 171                 } else
 172                         if (lines(fp, fn, off))
 173                                 return;
 174                 break;
 175         default:
 176                 break;
 177         }
 178
 179         while ((ch = getc(fp)) != EOF)
 180                 if (putchar(ch) == EOF)
 181                         oerr();
 182         if (ferror(fp)) {
 183                 ierr(fn);
 184                 return;
 185         }
 186         (void)fflush(stdout);
 187 }
 188
 189 /*
 190  * rlines -- display the last offset lines of the file.
 191  */
 192 static void
 193 rlines(FILE *fp, const char *fn, off_t off, struct stat *sbp)
 194 {
 195         struct mapinfo map;
 196         off_t curoff, size;
 197         int i;
 198
 199         if (!(size = sbp->st_size))
 200                 return;
 201         map.start = NULL;
 202         map.fd = fileno(fp);
 203         map.mapoff = map.maxoff = size;
 204
 205         /*
 206          * Last char is special, ignore whether newline or not. Note that
 207          * size == 0 is dealt with above, and size == 1 sets curoff to -1.
 208          */
 209         curoff = size - 2;
 210         while (curoff >= 0) {
 211                 if (curoff < map.mapoff && maparound(&map, curoff) != 0) {
 212                         ierr(fn);
 213                         return;
 214                 }
 215                 for (i = curoff - map.mapoff; i >= 0; i--)
 216                         if (map.start[i] == '\n' && --off == 0)
 217                                 break;
 218                 /* `i' is either the map offset of a '\n', or -1. */
 219                 curoff = map.mapoff + i;
 220                 if (i >= 0)
 221                         break;
 222         }
 223         curoff++;
 224         if (mapprint(&map, curoff, size - curoff) != 0) {
 225                 ierr(fn);
 226                 exit(1);
 227         }
 228
 229         /* Set the file pointer to reflect the length displayed. */
 230         if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) {
 231                 ierr(fn);
 232                 return;
 233         }
 234         if (map.start != NULL && munmap(map.start, map.maplen)) {
 235                 ierr(fn);
 236                 return;
 237         }
 238 }
 239
 240 static int
 241 show(file_info_t *file)
 242 {
 243         int ch;
 244
 245         while ((ch = getc(file->fp)) != EOF) {
 246                 if (last != file && no_files > 1) {
 247                         if (!qflag)
 248                                 printfn(file->file_name, 1);
 249                         last = file;
 250                 }
 251                 if (putchar(ch) == EOF)
 252                         oerr();
 253         }
 254         (void)fflush(stdout);
 255         if (ferror(file->fp)) {
 256                 fclose(file->fp);
 257                 file->fp = NULL;
 258                 ierr(file->file_name);
 259                 return 0;
 260         }
 261         clearerr(file->fp);
 262         return 1;
 263 }
 264
 265 static void
 266 set_events(file_info_t *files)
 267 {
 268         int i, n = 0;
 269         file_info_t *file;
 270         struct timespec ts;
 271         struct statfs sf;
 272
 273         ts.tv_sec = 0;
 274         ts.tv_nsec = 0;
 275
 276         action = USE_KQUEUE;
 277         for (i = 0, file = files; i < no_files; i++, file++) {
 278                 if (! file->fp)
 279                         continue;
 280
 281                 if (fstatfs(fileno(file->fp), &sf) == 0 &&
 282                     (sf.f_flags & MNT_LOCAL) == 0) {
 283                         action = USE_SLEEP;
 284                         return;
 285                 }
 286
 287                 if (Fflag && fileno(file->fp) != STDIN_FILENO) {
 288                         EV_SET(&ev[n], fileno(file->fp), EVFILT_VNODE,
 289                             EV_ADD | EV_ENABLE | EV_CLEAR,
 290                             NOTE_DELETE | NOTE_RENAME, 0, 0);
 291                         n++;
 292                 }
 293                 EV_SET(&ev[n], fileno(file->fp), EVFILT_READ,
 294                     EV_ADD | EV_ENABLE | EV_CLEAR, 0, 0, 0);
 295                 n++;
 296         }
 297
 298         if (kevent(kq, ev, n, NULL, 0, &ts) < 0) {
 299                 action = USE_SLEEP;
 300         }
 301 }
 302
 303 /*
 304  * follow -- display the file, from an offset, forward.
 305  *
 306  */
 307 void
 308 follow(file_info_t *files, enum STYLE style, off_t off)
 309 {
 310         int active, ev_change, i, n = -1;
 311         struct stat sb2;
 312         file_info_t *file;
 313         struct timespec ts;
 314
 315         /* Position each of the files */
 316
 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 (no_files > 1 && !qflag)
 325                                 printfn(file->file_name, 1);
 326                         forward(file->fp, file->file_name, style, off, &file->st);
 327                         if (Fflag && fileno(file->fp) != STDIN_FILENO)
 328                                 n++;
 329                 }
 330         }
 331         if (!Fflag && !active)
 332                 return;
 333
 334         last = --file;
 335
 336         kq = kqueue();
 337         if (kq < 0)
 338                 err(1, "kqueue");
 339         ev = malloc(n * sizeof(struct kevent));
 340         if (! ev)
 341             err(1, "Couldn't allocate memory for kevents.");
 342         set_events(files);
 343
 344         for (;;) {
 345                 ev_change = 0;
 346                 if (Fflag) {
 347                         for (i = 0, file = files; i < no_files; i++, file++) {
 348                                 if (!file->fp) {
 349                                         file->fp = fopen(file->file_name, "r");
 350                                         if (file->fp != NULL &&
 351                                             fstat(fileno(file->fp), &file->st)
 352                                             == -1) {
 353                                                 fclose(file->fp);
 354                                                 file->fp = NULL;
 355                                         }
 356                                         if (file->fp != NULL)
 357                                                 ev_change++;
 358                                         continue;
 359                                 }
 360                                 if (fileno(file->fp) == STDIN_FILENO)
 361                                         continue;
 362                                 if (stat(file->file_name, &sb2) == -1) {
 363                                         if (errno != ENOENT)
 364                                                 ierr(file->file_name);
 365                                         show(file);
 366                                         if (file->fp != NULL) {
 367                                                 fclose(file->fp);
 368                                                 file->fp = NULL;
 369                                         }
 370                                         ev_change++;
 371                                         continue;
 372                                 }
 373
 374                                 if (sb2.st_ino != file->st.st_ino ||
 375                                     sb2.st_dev != file->st.st_dev ||
 376                                     sb2.st_nlink == 0) {
 377                                         show(file);
 378                                         file->fp = freopen(file->file_name, "r",
 379                                             file->fp);
 380                                         if (file->fp != NULL)
 381                                                 memcpy(&file->st, &sb2,
 382                                                     sizeof(struct stat));
 383                                         else if (errno != ENOENT)
 384                                                 ierr(file->file_name);
 385                                         ev_change++;
 386                                 }
 387                         }
 388                 }
 389
 390                 for (i = 0, file = files; i < no_files; i++, file++)
 391                         if (file->fp && !show(file))
 392                                 ev_change++;
 393
 394                 if (ev_change)
 395                         set_events(files);
 396
 397                 switch (action) {
 398                 case USE_KQUEUE:
 399                         ts.tv_sec = 1;
 400                         ts.tv_nsec = 0;
 401                         /*
 402                          * In the -F case we set a timeout to ensure that
 403                          * we re-stat the file at least once every second.
 404                          */
 405                         n = kevent(kq, NULL, 0, ev, 1, Fflag ? &ts : NULL);
 406                         if (n < 0)
 407                                 err(1, "kevent");
 408                         if (n == 0) {
 409                                 /* timeout */
 410                                 break;
 411                         } else if (ev->filter == EVFILT_READ && ev->data < 0) {
 412                                 /* file shrank, reposition to end */
 413                                 if (lseek(ev->ident, (off_t)0, SEEK_END) == -1) {
 414                                         ierr(file->file_name);
 415                                         continue;
 416                                 }
 417                         }
 418                         break;
 419
 420                 case USE_SLEEP:
 421                         (void) usleep(250000);
 422                         break;
 423                 }
 424         }
 425 }