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