ea9bd2df1d
filesystem not being kq-aware), then fall back to using sleep. This allows tail to work with NFS filesystems again without chewing up CPU time. When given the -F flag, resort to sleep/stat after the file was moved or deleted. This allows a window where the file being tailed does not exist at all, which is typically the case during log rotation. Switch back to using kq (if possible) after the file is reopened.
311 lines
7.0 KiB
C
311 lines
7.0 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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* $FreeBSD$
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*/
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#ifndef lint
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static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93";
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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 kevent *evp[2];
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struct timespec ts = { 0, 0 };
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if (Fflag && fileno(fp) != STDIN_FILENO) {
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ev[n].ident = fileno(fp);
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ev[n].filter = EVFILT_VNODE;
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ev[n].flags = EV_ADD | EV_ENABLE | EV_CLEAR;
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ev[n].fflags = NOTE_DELETE | NOTE_RENAME;
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evp[n] = &ev[n];
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n++;
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}
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ev[n].ident = fileno(fp);
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ev[n].filter = EVFILT_READ;
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ev[n].flags = EV_ADD | EV_ENABLE;
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evp[n] = &ev[n];
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n++;
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if (kevent(kq, n, evp, 0, NULL, &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, 0, NULL, 1, ev, 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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register off_t size;
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register 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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