FreeBSD-5.3/usr.bin/tail/forward.c
/*-
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Edward Sze-Tyan Wang.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/usr.bin/tail/forward.c,v 1.33 2003/08/14 11:02:03 dg Exp $");
#ifndef lint
static const char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93";
#endif
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <sys/event.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "extern.h"
static void rlines(FILE *, off_t, struct stat *);
/* defines for inner loop actions */
#define USE_SLEEP 0
#define USE_KQUEUE 1
#define ADD_EVENTS 2
/*
* forward -- display the file, from an offset, forward.
*
* There are eight separate cases for this -- regular and non-regular
* files, by bytes or lines and from the beginning or end of the file.
*
* FBYTES byte offset from the beginning of the file
* REG seek
* NOREG read, counting bytes
*
* FLINES line offset from the beginning of the file
* REG read, counting lines
* NOREG read, counting lines
*
* RBYTES byte offset from the end of the file
* REG seek
* NOREG cyclically read characters into a wrap-around buffer
*
* RLINES
* REG mmap the file and step back until reach the correct offset.
* NOREG cyclically read lines into a wrap-around array of buffers
*/
void
forward(fp, style, off, sbp)
FILE *fp;
enum STYLE style;
off_t off;
struct stat *sbp;
{
int ch, n, kq = -1;
int action = USE_SLEEP;
struct kevent ev[2];
struct stat sb2;
struct timespec ts;
switch(style) {
case FBYTES:
if (off == 0)
break;
if (S_ISREG(sbp->st_mode)) {
if (sbp->st_size < off)
off = sbp->st_size;
if (fseeko(fp, off, SEEK_SET) == -1) {
ierr();
return;
}
} else while (off--)
if ((ch = getc(fp)) == EOF) {
if (ferror(fp)) {
ierr();
return;
}
break;
}
break;
case FLINES:
if (off == 0)
break;
for (;;) {
if ((ch = getc(fp)) == EOF) {
if (ferror(fp)) {
ierr();
return;
}
break;
}
if (ch == '\n' && !--off)
break;
}
break;
case RBYTES:
if (S_ISREG(sbp->st_mode)) {
if (sbp->st_size >= off &&
fseeko(fp, -off, SEEK_END) == -1) {
ierr();
return;
}
} else if (off == 0) {
while (getc(fp) != EOF);
if (ferror(fp)) {
ierr();
return;
}
} else
if (bytes(fp, off))
return;
break;
case RLINES:
if (S_ISREG(sbp->st_mode))
if (!off) {
if (fseeko(fp, (off_t)0, SEEK_END) == -1) {
ierr();
return;
}
} else
rlines(fp, off, sbp);
else if (off == 0) {
while (getc(fp) != EOF);
if (ferror(fp)) {
ierr();
return;
}
} else
if (lines(fp, off))
return;
break;
default:
break;
}
if (fflag) {
kq = kqueue();
if (kq < 0)
err(1, "kqueue");
action = ADD_EVENTS;
}
for (;;) {
while ((ch = getc(fp)) != EOF)
if (putchar(ch) == EOF)
oerr();
if (ferror(fp)) {
ierr();
return;
}
(void)fflush(stdout);
if (! fflag)
break;
clearerr(fp);
switch (action) {
case ADD_EVENTS:
n = 0;
ts.tv_sec = 0;
ts.tv_nsec = 0;
if (Fflag && fileno(fp) != STDIN_FILENO) {
EV_SET(&ev[n], fileno(fp), EVFILT_VNODE,
EV_ADD | EV_ENABLE | EV_CLEAR,
NOTE_DELETE | NOTE_RENAME, 0, 0);
n++;
}
EV_SET(&ev[n], fileno(fp), EVFILT_READ,
EV_ADD | EV_ENABLE | EV_CLEAR, 0, 0, 0);
n++;
if (kevent(kq, ev, n, NULL, 0, &ts) < 0) {
action = USE_SLEEP;
} else {
action = USE_KQUEUE;
}
break;
case USE_KQUEUE:
ts.tv_sec = 1;
ts.tv_nsec = 0;
/*
* In the -F case we set a timeout to ensure that
* we re-stat the file at least once every second.
*/
n = kevent(kq, NULL, 0, ev, 1, Fflag ? &ts : NULL);
if (n < 0)
err(1, "kevent");
if (n == 0) {
/* timeout */
break;
} else if (ev->filter == EVFILT_READ && ev->data < 0) {
/* file shrank, reposition to end */
if (fseeko(fp, (off_t)0, SEEK_END) == -1) {
ierr();
return;
}
}
break;
case USE_SLEEP:
(void) usleep(250000);
clearerr(fp);
break;
}
if (Fflag && fileno(fp) != STDIN_FILENO) {
while (stat(fname, &sb2) != 0)
/* file was rotated, wait until it reappears */
(void)sleep(1);
if (sb2.st_ino != sbp->st_ino ||
sb2.st_dev != sbp->st_dev ||
sb2.st_nlink == 0) {
fp = freopen(fname, "r", fp);
if (fp == NULL) {
ierr();
return;
} else {
*sbp = sb2;
action = ADD_EVENTS;
}
}
}
}
}
/*
* rlines -- display the last offset lines of the file.
*/
static void
rlines(fp, off, sbp)
FILE *fp;
off_t off;
struct stat *sbp;
{
struct mapinfo map;
off_t curoff, size;
int i;
if (!(size = sbp->st_size))
return;
map.start = NULL;
map.fd = fileno(fp);
map.mapoff = map.maxoff = size;
/*
* Last char is special, ignore whether newline or not. Note that
* size == 0 is dealt with above, and size == 1 sets curoff to -1.
*/
curoff = size - 2;
while (curoff >= 0) {
if (curoff < map.mapoff && maparound(&map, curoff) != 0) {
ierr();
return;
}
for (i = curoff - map.mapoff; i >= 0; i--)
if (map.start[i] == '\n' && --off == 0)
break;
/* `i' is either the map offset of a '\n', or -1. */
curoff = map.mapoff + i;
if (i >= 0)
break;
}
curoff++;
if (mapprint(&map, curoff, size - curoff) != 0) {
ierr();
exit(1);
}
/* Set the file pointer to reflect the length displayed. */
if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) {
ierr();
return;
}
if (map.start != NULL && munmap(map.start, map.maplen)) {
ierr();
return;
}
}