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  * 4. 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
  33 #include <sys/cdefs.h>
  34
  35 __FBSDID("$FreeBSD$");
  36
  37 #ifndef lint
  38 static const char sccsid[] = "@(#)forward.c     8.1 (Berkeley) 6/6/93";
  39 #endif
  40
  41 #include <sys/param.h>
  42 #include <sys/mount.h>
  43 #include <sys/types.h>
  44 #include <sys/stat.h>
  45 #include <sys/time.h>
  46 #include <sys/mman.h>
  47 #include <sys/event.h>
  48
  49 #include <err.h>
  50 #include <errno.h>
  51 #include <fcntl.h>
  52 #include <limits.h>
  53 #include <stdio.h>
  54 #include <stdlib.h>
  55 #include <string.h>
  56 #include <unistd.h>
  57
  58 #include "extern.h"
  59
  60 static void rlines(FILE *, const char *fn, off_t, struct stat *);
  61 static int show(file_info_t *);
  62 static void set_events(file_info_t *files);
  63
  64 /* defines for inner loop actions */
  65 #define USE_SLEEP       0
  66 #define USE_KQUEUE      1
  67 #define ADD_EVENTS      2
  68
  69 struct kevent *ev;
  70 int action = USE_SLEEP;
  71 int kq;
  72
  73 static const file_info_t *last;
  74
  75 /*
  76  * forward -- display the file, from an offset, forward.
  77  *
  78  * There are eight separate cases for this -- regular and non-regular
  79  * files, by bytes or lines and from the beginning or end of the file.
  80  *
  81  * FBYTES       byte offset from the beginning of the file
  82  *      REG     seek
  83  *      NOREG   read, counting bytes
  84  *
  85  * FLINES       line offset from the beginning of the file
  86  *      REG     read, counting lines
  87  *      NOREG   read, counting lines
  88  *
  89  * RBYTES       byte offset from the end of the file
  90  *      REG     seek
  91  *      NOREG   cyclically read characters into a wrap-around buffer
  92  *
  93  * RLINES
  94  *      REG     mmap the file and step back until reach the correct offset.
  95  *      NOREG   cyclically read lines into a wrap-around array of buffers
  96  */
  97 void
  98 forward(FILE *fp, const char *fn, enum STYLE style, off_t off, struct stat *sbp)
  99 {
 100         int ch;
 101
 102         switch(style) {
 103         case FBYTES:
 104                 if (off == 0)
 105                         break;
 106                 if (S_ISREG(sbp->st_mode)) {
 107                         if (sbp->st_size < off)
 108                                 off = sbp->st_size;
 109                         if (fseeko(fp, off, SEEK_SET) == -1) {
 110                                 ierr(fn);
 111                                 return;
 112                         }
 113                 } else while (off--)
 114                         if ((ch = getc(fp)) == EOF) {
 115                                 if (ferror(fp)) {
 116                                         ierr(fn);
 117                                         return;
 118                                 }
 119                                 break;
 120                         }
 121                 break;
 122         case FLINES:
 123                 if (off == 0)
 124                         break;
 125                 for (;;) {
 126                         if ((ch = getc(fp)) == EOF) {
 127                                 if (ferror(fp)) {
 128                                         ierr(fn);
 129                                         return;
 130                                 }
 131                                 break;
 132                         }
 133                         if (ch == '\n' && !--off)
 134                                 break;
 135                 }
 136                 break;
 137         case RBYTES:
 138                 if (S_ISREG(sbp->st_mode)) {
 139                         if (sbp->st_size >= off &&
 140                             fseeko(fp, -off, SEEK_END) == -1) {
 141                                 ierr(fn);
 142                                 return;
 143                         }
 144                 } else if (off == 0) {
 145                         while (getc(fp) != EOF);
 146                         if (ferror(fp)) {
 147                                 ierr(fn);
 148                                 return;
 149                         }
 150                 } else
 151                         if (bytes(fp, fn, off))
 152                                 return;
 153                 break;
 154         case RLINES:
 155                 if (S_ISREG(sbp->st_mode))
 156                         if (!off) {
 157                                 if (fseeko(fp, (off_t)0, SEEK_END) == -1) {
 158                                         ierr(fn);
 159                                         return;
 160                                 }
 161                         } else
 162                                 rlines(fp, fn, off, sbp);
 163                 else if (off == 0) {
 164                         while (getc(fp) != EOF);
 165                         if (ferror(fp)) {
 166                                 ierr(fn);
 167                                 return;
 168                         }
 169                 } else
 170                         if (lines(fp, fn, off))
 171                                 return;
 172                 break;
 173         default:
 174                 break;
 175         }
 176
 177         while ((ch = getc(fp)) != EOF)
 178                 if (putchar(ch) == EOF)
 179                         oerr();
 180         if (ferror(fp)) {
 181                 ierr(fn);
 182                 return;
 183         }
 184         (void)fflush(stdout);
 185 }
 186
 187 /*
 188  * rlines -- display the last offset lines of the file.
 189  */
 190 static void
 191 rlines(FILE *fp, const char *fn, off_t off, struct stat *sbp)
 192 {
 193         struct mapinfo map;
 194         off_t curoff, size;
 195         int i;
 196
 197         if (!(size = sbp->st_size))
 198                 return;
 199         map.start = NULL;
 200         map.fd = fileno(fp);
 201         map.mapoff = map.maxoff = size;
 202
 203         /*
 204          * Last char is special, ignore whether newline or not. Note that
 205          * size == 0 is dealt with above, and size == 1 sets curoff to -1.
 206          */
 207         curoff = size - 2;
 208         while (curoff >= 0) {
 209                 if (curoff < map.mapoff && maparound(&map, curoff) != 0) {
 210                         ierr(fn);
 211                         return;
 212                 }
 213                 for (i = curoff - map.mapoff; i >= 0; i--)
 214                         if (map.start[i] == '\n' && --off == 0)
 215                                 break;
 216                 /* `i' is either the map offset of a '\n', or -1. */
 217                 curoff = map.mapoff + i;
 218                 if (i >= 0)
 219                         break;
 220         }
 221         curoff++;
 222         if (mapprint(&map, curoff, size - curoff) != 0) {
 223                 ierr(fn);
 224                 exit(1);
 225         }
 226
 227         /* Set the file pointer to reflect the length displayed. */
 228         if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) {
 229                 ierr(fn);
 230                 return;
 231         }
 232         if (map.start != NULL && munmap(map.start, map.maplen)) {
 233                 ierr(fn);
 234                 return;
 235         }
 236 }
 237
 238 static int
 239 show(file_info_t *file)
 240 {
 241         int ch;
 242
 243         while ((ch = getc(file->fp)) != EOF) {
 244                 if (last != file && no_files > 1) {
 245                         if (!qflag)
 246                                 (void)printf("\n==> %s <==\n", file->file_name);
 247                         last = file;
 248                 }
 249                 if (putchar(ch) == EOF)
 250                         oerr();
 251         }
 252         (void)fflush(stdout);
 253         if (ferror(file->fp)) {
 254                 fclose(file->fp);
 255                 file->fp = NULL;
 256                 ierr(file->file_name);
 257                 return 0;
 258         }
 259         clearerr(file->fp);
 260         return 1;
 261 }
 262
 263 static void
 264 set_events(file_info_t *files)
 265 {
 266         int i, n = 0;
 267         file_info_t *file;
 268         struct timespec ts;
 269         struct statfs sf;
 270
 271         ts.tv_sec = 0;
 272         ts.tv_nsec = 0;
 273
 274         action = USE_KQUEUE;
 275         for (i = 0, file = files; i < no_files; i++, file++) {
 276                 if (! file->fp)
 277                         continue;
 278
 279                 if (fstatfs(fileno(file->fp), &sf) == 0 &&
 280                     (sf.f_flags & MNT_LOCAL) == 0) {
 281                         action = USE_SLEEP;
 282                         return;
 283                 }
 284
 285                 if (Fflag && fileno(file->fp) != STDIN_FILENO) {
 286                         EV_SET(&ev[n], fileno(file->fp), EVFILT_VNODE,
 287                             EV_ADD | EV_ENABLE | EV_CLEAR,
 288                             NOTE_DELETE | NOTE_RENAME, 0, 0);
 289                         n++;
 290                 }
 291                 EV_SET(&ev[n], fileno(file->fp), EVFILT_READ,
 292                     EV_ADD | EV_ENABLE | EV_CLEAR, 0, 0, 0);
 293                 n++;
 294         }
 295
 296         if (kevent(kq, ev, n, NULL, 0, &ts) < 0) {
 297                 action = USE_SLEEP;
 298         }
 299 }
 300
 301 /*
 302  * follow -- display the file, from an offset, forward.
 303  *
 304  */
 305 void
 306 follow(file_info_t *files, enum STYLE style, off_t off)
 307 {
 308         int active, ev_change, i, n = -1;
 309         struct stat sb2;
 310         file_info_t *file;
 311         struct timespec ts;
 312
 313         /* Position each of the files */
 314
 315         file = files;
 316         active = 0;
 317         n = 0;
 318         for (i = 0; i < no_files; i++, file++) {
 319                 if (file->fp) {
 320                         active = 1;
 321                         n++;
 322                         if (no_files > 1 && !qflag)
 323                                 (void)printf("\n==> %s <==\n", file->file_name);
 324                         forward(file->fp, file->file_name, style, off, &file->st);
 325                         if (Fflag && fileno(file->fp) != STDIN_FILENO)
 326                                 n++;
 327                 }
 328         }
 329         if (!Fflag && !active)
 330                 return;
 331
 332         last = --file;
 333
 334         kq = kqueue();
 335         if (kq < 0)
 336                 err(1, "kqueue");
 337         ev = malloc(n * sizeof(struct kevent));
 338         if (! ev)
 339             err(1, "Couldn't allocate memory for kevents.");
 340         set_events(files);
 341
 342         for (;;) {
 343                 ev_change = 0;
 344                 if (Fflag) {
 345                         for (i = 0, file = files; i < no_files; i++, file++) {
 346                                 if (!file->fp) {
 347                                         file->fp = fopen(file->file_name, "r");
 348                                         if (file->fp != NULL &&
 349                                             fstat(fileno(file->fp), &file->st)
 350                                             == -1) {
 351                                                 fclose(file->fp);
 352                                                 file->fp = NULL;
 353                                         }
 354                                         if (file->fp != NULL)
 355                                                 ev_change++;
 356                                         continue;
 357                                 }
 358                                 if (fileno(file->fp) == STDIN_FILENO)
 359                                         continue;
 360                                 if (stat(file->file_name, &sb2) == -1) {
 361                                         if (errno != ENOENT)
 362                                                 ierr(file->file_name);
 363                                         show(file);
 364                                         if (file->fp != NULL) {
 365                                                 fclose(file->fp);
 366                                                 file->fp = NULL;
 367                                         }
 368                                         ev_change++;
 369                                         continue;
 370                                 }
 371
 372                                 if (sb2.st_ino != file->st.st_ino ||
 373                                     sb2.st_dev != file->st.st_dev ||
 374                                     sb2.st_nlink == 0) {
 375                                         show(file);
 376                                         file->fp = freopen(file->file_name, "r",
 377                                             file->fp);
 378                                         if (file->fp != NULL)
 379                                                 memcpy(&file->st, &sb2,
 380                                                     sizeof(struct stat));
 381                                         else if (errno != ENOENT)
 382                                                 ierr(file->file_name);
 383                                         ev_change++;
 384                                 }
 385                         }
 386                 }
 387
 388                 for (i = 0, file = files; i < no_files; i++, file++)
 389                         if (file->fp && !show(file))
 390                                 ev_change++;
 391
 392                 if (ev_change)
 393                         set_events(files);
 394
 395                 switch (action) {
 396                 case USE_KQUEUE:
 397                         ts.tv_sec = 1;
 398                         ts.tv_nsec = 0;
 399                         /*
 400                          * In the -F case we set a timeout to ensure that
 401                          * we re-stat the file at least once every second.
 402                          */
 403                         n = kevent(kq, NULL, 0, ev, 1, Fflag ? &ts : NULL);
 404                         if (n < 0)
 405                                 err(1, "kevent");
 406                         if (n == 0) {
 407                                 /* timeout */
 408                                 break;
 409                         } else if (ev->filter == EVFILT_READ && ev->data < 0) {
 410                                 /* file shrank, reposition to end */
 411                                 if (lseek(ev->ident, (off_t)0, SEEK_END) == -1) {
 412                                         ierr(file->file_name);
 413                                         continue;
 414                                 }
 415                         }
 416                         break;
 417
 418                 case USE_SLEEP:
 419                         (void) usleep(250000);
 420                         break;
 421                 }
 422         }
 423 }