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