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
  36
  37 #include <sys/param.h>
  38 #include <sys/mount.h>
  39 #include <sys/types.h>
  40 #include <sys/stat.h>
  41 #include <sys/time.h>
  42 #include <sys/mman.h>
  43 #include <sys/event.h>
  44
  45 #include <err.h>
  46 #include <errno.h>
  47 #include <fcntl.h>
  48 #include <limits.h>
  49 #include <stdio.h>
  50 #include <stdlib.h>
  51 #include <string.h>
  52 #include <unistd.h>
  53
  54 #include <libcasper.h>
  55 #include <casper/cap_fileargs.h>
  56
  57 #include "extern.h"
  58
  59 static void rlines(FILE *, const char *fn, off_t, struct stat *);
  60 static int show(file_info_t *);
  61 static void set_events(file_info_t *files);
  62
  63 /* defines for inner loop actions */
  64 #define USE_SLEEP       0
  65 #define USE_KQUEUE      1
  66 #define ADD_EVENTS      2
  67
  68 static struct kevent *ev;
  69 static int action = USE_SLEEP;
  70 static int kq;
  71
  72 static const file_info_t *last;
  73
  74 /*
  75  * forward -- display the file, from an offset, forward.
  76  *
  77  * There are eight separate cases for this -- regular and non-regular
  78  * files, by bytes or lines and from the beginning or end of the file.
  79  *
  80  * FBYTES       byte offset from the beginning of the file
  81  *      REG     seek
  82  *      NOREG   read, counting bytes
  83  *
  84  * FLINES       line offset from the beginning of the file
  85  *      REG     read, counting lines
  86  *      NOREG   read, counting lines
  87  *
  88  * RBYTES       byte offset from the end of the file
  89  *      REG     seek
  90  *      NOREG   cyclically read characters into a wrap-around buffer
  91  *
  92  * RLINES
  93  *      REG     mmap the file and step back until reach the correct offset.
  94  *      NOREG   cyclically read lines into a wrap-around array of buffers
  95  */
  96 void
  97 forward(FILE *fp, const char *fn, enum STYLE style, off_t off, struct stat *sbp)
  98 {
  99         int ch;
 100
 101         switch(style) {
 102         case FBYTES:
 103                 if (off == 0)
 104                         break;
 105                 if (S_ISREG(sbp->st_mode)) {
 106                         if (sbp->st_size < off)
 107                                 off = sbp->st_size;
 108                         if (fseeko(fp, off, SEEK_SET) == -1) {
 109                                 ierr(fn);
 110                                 return;
 111                         }
 112                 } else while (off--)
 113                         if ((ch = getc(fp)) == EOF) {
 114                                 if (ferror(fp)) {
 115                                         ierr(fn);
 116                                         return;
 117                                 }
 118                                 break;
 119                         }
 120                 break;
 121         case FLINES:
 122                 if (off == 0)
 123                         break;
 124                 for (;;) {
 125                         if ((ch = getc(fp)) == EOF) {
 126                                 if (ferror(fp)) {
 127                                         ierr(fn);
 128                                         return;
 129                                 }
 130                                 break;
 131                         }
 132                         if (ch == '\n' && !--off)
 133                                 break;
 134                 }
 135                 break;
 136         case RBYTES:
 137                 if (S_ISREG(sbp->st_mode)) {
 138                         if (sbp->st_size >= off &&
 139                             fseeko(fp, -off, SEEK_END) == -1) {
 140                                 ierr(fn);
 141                                 return;
 142                         }
 143                 } else if (off == 0) {
 144                         while (getc(fp) != EOF);
 145                         if (ferror(fp)) {
 146                                 ierr(fn);
 147                                 return;
 148                         }
 149                 } else
 150                         if (bytes(fp, fn, off))
 151                                 return;
 152                 break;
 153         case RLINES:
 154                 if (S_ISREG(sbp->st_mode))
 155                         if (!off) {
 156                                 if (fseeko(fp, (off_t)0, SEEK_END) == -1) {
 157                                         ierr(fn);
 158                                         return;
 159                                 }
 160                         } else
 161                                 rlines(fp, fn, off, sbp);
 162                 else if (off == 0) {
 163                         while (getc(fp) != EOF);
 164                         if (ferror(fp)) {
 165                                 ierr(fn);
 166                                 return;
 167                         }
 168                 } else
 169                         if (lines(fp, fn, off))
 170                                 return;
 171                 break;
 172         default:
 173                 break;
 174         }
 175
 176         while ((ch = getc(fp)) != EOF)
 177                 if (putchar(ch) == EOF)
 178                         oerr();
 179         if (ferror(fp)) {
 180                 ierr(fn);
 181                 return;
 182         }
 183         (void)fflush(stdout);
 184 }
 185
 186 /*
 187  * rlines -- display the last offset lines of the file.
 188  */
 189 static void
 190 rlines(FILE *fp, const char *fn, off_t off, struct stat *sbp)
 191 {
 192         struct mapinfo map;
 193         off_t curoff, size;
 194         int i;
 195
 196         if (!(size = sbp->st_size))
 197                 return;
 198         map.start = NULL;
 199         map.fd = fileno(fp);
 200         map.mapoff = map.maxoff = size;
 201
 202         /*
 203          * Last char is special, ignore whether newline or not. Note that
 204          * size == 0 is dealt with above, and size == 1 sets curoff to -1.
 205          */
 206         curoff = size - 2;
 207         while (curoff >= 0) {
 208                 if (curoff < map.mapoff && maparound(&map, curoff) != 0) {
 209                         ierr(fn);
 210                         return;
 211                 }
 212                 for (i = curoff - map.mapoff; i >= 0; i--)
 213                         if (map.start[i] == '\n' && --off == 0)
 214                                 break;
 215                 /* `i' is either the map offset of a '\n', or -1. */
 216                 curoff = map.mapoff + i;
 217                 if (i >= 0)
 218                         break;
 219         }
 220         curoff++;
 221         if (mapprint(&map, curoff, size - curoff) != 0) {
 222                 ierr(fn);
 223                 exit(1);
 224         }
 225
 226         /* Set the file pointer to reflect the length displayed. */
 227         if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) {
 228                 ierr(fn);
 229                 return;
 230         }
 231         if (map.start != NULL && munmap(map.start, map.maplen)) {
 232                 ierr(fn);
 233                 return;
 234         }
 235 }
 236
 237 static int
 238 show(file_info_t *file)
 239 {
 240         int ch;
 241
 242         while ((ch = getc(file->fp)) != EOF) {
 243                 if (last != file) {
 244                         if (vflag || (qflag == 0 && no_files > 1))
 245                                 printfn(file->file_name, 1);
 246                         last = file;
 247                 }
 248                 if (putchar(ch) == EOF)
 249                         oerr();
 250         }
 251         (void)fflush(stdout);
 252         if (ferror(file->fp)) {
 253                 fclose(file->fp);
 254                 file->fp = NULL;
 255                 ierr(file->file_name);
 256                 return 0;
 257         }
 258         clearerr(file->fp);
 259         return 1;
 260 }
 261
 262 static void
 263 set_events(file_info_t *files)
 264 {
 265         int i, n = 0;
 266         file_info_t *file;
 267         struct timespec ts;
 268         struct statfs sf;
 269
 270         ts.tv_sec = 0;
 271         ts.tv_nsec = 0;
 272
 273         action = USE_KQUEUE;
 274         for (i = 0, file = files; i < no_files; i++, file++) {
 275                 if (!file->fp)
 276                         continue;
 277
 278                 if (fstatfs(fileno(file->fp), &sf) == 0 &&
 279                     (sf.f_flags & MNT_LOCAL) == 0) {
 280                         action = USE_SLEEP;
 281                         return;
 282                 }
 283
 284                 if (Fflag && fileno(file->fp) != STDIN_FILENO) {
 285                         EV_SET(&ev[n], fileno(file->fp), EVFILT_VNODE,
 286                             EV_ADD | EV_ENABLE | EV_CLEAR,
 287                             NOTE_DELETE | NOTE_RENAME, 0, 0);
 288                         n++;
 289                 }
 290                 EV_SET(&ev[n], fileno(file->fp), EVFILT_READ,
 291                     EV_ADD | EV_ENABLE | EV_CLEAR, 0, 0, 0);
 292                 n++;
 293         }
 294
 295         if (kevent(kq, ev, n, NULL, 0, &ts) < 0) {
 296                 action = USE_SLEEP;
 297         }
 298 }
 299
 300 /*
 301  * follow -- display the file, from an offset, forward.
 302  *
 303  */
 304 void
 305 follow(file_info_t *files, enum STYLE style, off_t off)
 306 {
 307         int active, ev_change, i, n;
 308         struct stat sb2;
 309         file_info_t *file;
 310         FILE *ftmp;
 311         struct timespec ts;
 312
 313         /* Position each of the files */
 314         active = 0;
 315         for (i = 0, file = files; i < no_files; i++, file++) {
 316                 if (!file->fp)
 317                         continue;
 318                 active = 1;
 319                 if (vflag || (qflag == 0 && no_files > 1))
 320                         printfn(file->file_name, 1);
 321                 forward(file->fp, file->file_name, style, off, &file->st);
 322         }
 323         if (!Fflag && !active)
 324                 return;
 325
 326         last = --file;
 327
 328         kq = kqueue();
 329         if (kq < 0)
 330                 err(1, "kqueue");
 331         /*
 332          * The number of kqueue events we track may vary over time and may
 333          * even grow past its initial value in the -F case, but it will
 334          * never exceed two per file, so just preallocate that.
 335          */
 336         ev = malloc(no_files * 2 * sizeof(struct kevent));
 337         if (ev == NULL)
 338                 err(1, "failed to allocate memory for kevents");
 339         set_events(files);
 340
 341         for (;;) {
 342                 ev_change = 0;
 343                 if (Fflag) {
 344                         for (i = 0, file = files; i < no_files; i++, file++) {
 345                                 if (!file->fp) {
 346                                         file->fp =
 347                                             fileargs_fopen(fa, file->file_name,
 348                                             "r");
 349                                         if (file->fp != NULL &&
 350                                             fstat(fileno(file->fp), &file->st)
 351                                             == -1) {
 352                                                 fclose(file->fp);
 353                                                 file->fp = NULL;
 354                                         }
 355                                         if (file->fp != NULL)
 356                                                 ev_change++;
 357                                         continue;
 358                                 }
 359                                 if (fileno(file->fp) == STDIN_FILENO)
 360                                         continue;
 361                                 ftmp = fileargs_fopen(fa, file->file_name, "r");
 362                                 if (ftmp == NULL ||
 363                                     fstat(fileno(ftmp), &sb2) == -1) {
 364                                         if (errno != ENOENT)
 365                                                 ierr(file->file_name);
 366                                         show(file);
 367                                         if (file->fp != NULL) {
 368                                                 fclose(file->fp);
 369                                                 file->fp = NULL;
 370                                         }
 371                                         if (ftmp != NULL) {
 372                                                 fclose(ftmp);
 373                                         }
 374                                         ev_change++;
 375                                         continue;
 376                                 }
 377
 378                                 if (sb2.st_ino != file->st.st_ino ||
 379                                     sb2.st_dev != file->st.st_dev ||
 380                                     sb2.st_nlink == 0) {
 381                                         show(file);
 382                                         fclose(file->fp);
 383                                         file->fp = ftmp;
 384                                         memcpy(&file->st, &sb2,
 385                                             sizeof(struct stat));
 386                                         ev_change++;
 387                                 } else {
 388                                         fclose(ftmp);
 389                                 }
 390                         }
 391                 }
 392
 393                 for (i = 0, file = files; i < no_files; i++, file++)
 394                         if (file->fp && !show(file))
 395                                 ev_change++;
 396
 397                 if (ev_change)
 398                         set_events(files);
 399
 400                 switch (action) {
 401                 case USE_KQUEUE:
 402                         ts.tv_sec = 1;
 403                         ts.tv_nsec = 0;
 404                         /*
 405                          * In the -F case we set a timeout to ensure that
 406                          * we re-stat the file at least once every second.
 407                          * If we've received EINTR, ignore it. Both reasons
 408                          * for its generation are transient.
 409                          */
 410                         do {
 411                                 n = kevent(kq, NULL, 0, ev, 1, Fflag ? &ts : NULL);
 412                                 if (n < 0 && errno != EINTR)
 413                                         err(1, "kevent");
 414                         } while (n < 0);
 415                         if (n == 0) {
 416                                 /* timeout */
 417                                 break;
 418                         } else if (ev->filter == EVFILT_READ && ev->data < 0) {
 419                                 /* file shrank, reposition to end */
 420                                 if (lseek(ev->ident, (off_t)0, SEEK_END) == -1) {
 421                                         ierr(file->file_name);
 422                                         continue;
 423                                 }
 424                         }
 425                         break;
 426
 427                 case USE_SLEEP:
 428                         (void) usleep(250000);
 429                         break;
 430                 }
 431         }
 432 }