308 lines
6.9 KiB
C
308 lines
6.9 KiB
C
/*-
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* Copyright (c) 1991, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Edward Sze-Tyan Wang.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef lint
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#if 0
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static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93";
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#endif
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static const char rcsid[] =
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"$FreeBSD$";
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#endif /* not lint */
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/time.h>
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#include <sys/mman.h>
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#include <sys/event.h>
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#include <limits.h>
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#include <fcntl.h>
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#include <errno.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <err.h>
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#include "extern.h"
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static void rlines __P((FILE *, long, struct stat *));
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/* defines for inner loop actions */
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#define USE_SLEEP 0
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#define USE_KQUEUE 1
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#define ADD_EVENTS 2
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/*
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* forward -- display the file, from an offset, forward.
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*
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* There are eight separate cases for this -- regular and non-regular
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* files, by bytes or lines and from the beginning or end of the file.
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*
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* FBYTES byte offset from the beginning of the file
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* REG seek
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* NOREG read, counting bytes
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*
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* FLINES line offset from the beginning of the file
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* REG read, counting lines
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* NOREG read, counting lines
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*
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* RBYTES byte offset from the end of the file
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* REG seek
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* NOREG cyclically read characters into a wrap-around buffer
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*
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* RLINES
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* REG mmap the file and step back until reach the correct offset.
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* NOREG cyclically read lines into a wrap-around array of buffers
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*/
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void
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forward(fp, style, off, sbp)
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FILE *fp;
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enum STYLE style;
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long off;
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struct stat *sbp;
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{
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int ch, kq = -1;
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int action = USE_SLEEP;
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struct kevent ev[2];
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struct stat sb2;
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switch(style) {
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case FBYTES:
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if (off == 0)
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break;
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if (S_ISREG(sbp->st_mode)) {
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if (sbp->st_size < off)
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off = sbp->st_size;
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if (fseek(fp, off, SEEK_SET) == -1) {
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ierr();
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return;
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}
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} else while (off--)
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if ((ch = getc(fp)) == EOF) {
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if (ferror(fp)) {
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ierr();
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return;
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}
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break;
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}
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break;
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case FLINES:
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if (off == 0)
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break;
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for (;;) {
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if ((ch = getc(fp)) == EOF) {
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if (ferror(fp)) {
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ierr();
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return;
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}
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break;
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}
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if (ch == '\n' && !--off)
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break;
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}
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break;
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case RBYTES:
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if (S_ISREG(sbp->st_mode)) {
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if (sbp->st_size >= off &&
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fseek(fp, -off, SEEK_END) == -1) {
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ierr();
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return;
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}
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} else if (off == 0) {
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while (getc(fp) != EOF);
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if (ferror(fp)) {
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ierr();
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return;
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}
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} else
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if (bytes(fp, off))
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return;
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break;
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case RLINES:
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if (S_ISREG(sbp->st_mode))
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if (!off) {
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if (fseek(fp, 0L, SEEK_END) == -1) {
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ierr();
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return;
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}
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} else
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rlines(fp, off, sbp);
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else if (off == 0) {
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while (getc(fp) != EOF);
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if (ferror(fp)) {
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ierr();
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return;
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}
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} else
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if (lines(fp, off))
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return;
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break;
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}
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if (fflag) {
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kq = kqueue();
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if (kq < 0)
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err(1, "kqueue");
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action = ADD_EVENTS;
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}
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for (;;) {
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while ((ch = getc(fp)) != EOF)
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if (putchar(ch) == EOF)
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oerr();
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if (ferror(fp)) {
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ierr();
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return;
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}
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(void)fflush(stdout);
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if (! fflag)
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break;
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clearerr(fp);
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switch (action) {
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case ADD_EVENTS: {
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int n = 0;
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struct timespec ts = { 0, 0 };
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if (Fflag && fileno(fp) != STDIN_FILENO) {
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EV_SET(&ev[n], fileno(fp), EVFILT_VNODE,
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EV_ADD | EV_ENABLE | EV_CLEAR,
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NOTE_DELETE | NOTE_RENAME, 0, 0);
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n++;
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}
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EV_SET(&ev[n], fileno(fp), EVFILT_READ,
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EV_ADD | EV_ENABLE, 0, 0, 0);
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n++;
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if (kevent(kq, ev, n, NULL, 0, &ts) < 0) {
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close(kq);
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kq = -1;
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action = USE_SLEEP;
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} else {
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action = USE_KQUEUE;
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}
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break;
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}
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case USE_KQUEUE:
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if (kevent(kq, NULL, 0, ev, 1, NULL) < 0)
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err(1, "kevent");
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if (ev->filter == EVFILT_VNODE) {
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/* file was rotated, wait until it reappears */
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action = USE_SLEEP;
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} else if (ev->data < 0) {
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/* file shrank, reposition to end */
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if (fseek(fp, 0L, SEEK_END) == -1) {
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ierr();
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return;
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}
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}
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break;
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case USE_SLEEP:
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(void) usleep(250000);
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clearerr(fp);
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if (Fflag && fileno(fp) != STDIN_FILENO &&
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stat(fname, &sb2) != -1) {
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if (sb2.st_ino != sbp->st_ino ||
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sb2.st_dev != sbp->st_dev ||
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sb2.st_rdev != sbp->st_rdev ||
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sb2.st_nlink == 0) {
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fp = freopen(fname, "r", fp);
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if (fp == NULL) {
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ierr();
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break;
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}
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*sbp = sb2;
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if (kq != -1)
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action = ADD_EVENTS;
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}
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}
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break;
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}
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}
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}
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/*
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* rlines -- display the last offset lines of the file.
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*/
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static void
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rlines(fp, off, sbp)
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FILE *fp;
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long off;
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struct stat *sbp;
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{
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off_t size;
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char *p;
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char *start;
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if (!(size = sbp->st_size))
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return;
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if (size > SIZE_T_MAX) {
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errno = EFBIG;
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ierr();
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return;
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}
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if ((start = mmap(NULL, (size_t)size,
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PROT_READ, MAP_SHARED, fileno(fp), (off_t)0)) == MAP_FAILED) {
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ierr();
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return;
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}
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/* Last char is special, ignore whether newline or not. */
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for (p = start + size - 1; --size;)
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if (*--p == '\n' && !--off) {
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++p;
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break;
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}
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/* Set the file pointer to reflect the length displayed. */
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size = sbp->st_size - size;
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WR(p, size);
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if (fseek(fp, (long)sbp->st_size, SEEK_SET) == -1) {
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ierr();
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return;
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}
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if (munmap(start, (size_t)sbp->st_size)) {
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ierr();
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return;
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}
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}
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