OpenBSD-4.6/usr.bin/tail/forward.c
/* $OpenBSD: forward.c,v 1.25 2008/11/13 18:33:03 landry Exp $ */
/* $NetBSD: forward.c,v 1.7 1996/02/13 16:49:10 ghudson Exp $ */
/*-
* 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. 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.
*/
#ifndef lint
#if 0
static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93";
#endif
static char rcsid[] = "$OpenBSD: forward.c,v 1.25 2008/11/13 18:33:03 landry Exp $";
#endif /* not lint */
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/event.h>
#include <err.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include "extern.h"
static int rlines(FILE *, off_t, struct stat *);
/*
* 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 step back until the correct offset is reached.
* NOREG cyclically read lines into a wrap-around array of buffers
*/
void
forward(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
{
int ch;
struct stat nsb;
int kq, queue;
struct kevent ke;
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 if (rlines(fp, off, sbp) != 0)
lines(fp, off);
} else if (off == 0) {
while (getc(fp) != EOF)
;
if (ferror(fp)) {
ierr();
return;
}
} else {
if (lines(fp, off))
return;
}
break;
}
kq = -1;
kq_retry:
if (fflag && ((kq = kqueue()) >= 0)) {
EV_SET(&ke, fileno(fp), EVFILT_READ,
EV_ENABLE | EV_ADD | EV_CLEAR,
0,
0, NULL);
if (kevent(kq, &ke, 1, NULL, 0, NULL) < 0) {
close(kq);
kq = -1;
} else if (S_ISREG(sbp->st_mode)) {
EV_SET(&ke, fileno(fp), EVFILT_VNODE,
EV_ENABLE | EV_ADD | EV_CLEAR,
NOTE_DELETE | NOTE_RENAME | NOTE_TRUNCATE,
0, NULL);
if (kevent(kq, &ke, 1, NULL, 0, NULL) < 0) {
close(kq);
kq = -1;
}
}
}
for (;;) {
while (!feof(fp) && (ch = getc(fp)) != EOF)
if (putchar(ch) == EOF)
oerr();
if (ferror(fp)) {
ierr();
if (kq != -1)
close(kq);
return;
}
(void)fflush(stdout);
if (!fflag)
break;
clearerr(fp);
queue = 1;
if (kq < 0 || kevent(kq, NULL, 0, &ke, 1, NULL) <= 0) {
queue = 0;
sleep(1);
} else if (ke.filter == EVFILT_READ) {
continue;
} else if ((ke.fflags & NOTE_TRUNCATE) == 0) {
/*
* File was renamed or deleted.
*
* Continue to look at it until a new file reappears
* with the same name.
* Fall back to the old algorithm for that.
*/
close(kq);
kq = -1;
}
if (is_stdin || stat(fname, &nsb) != 0)
continue;
/* Reopen file if the inode changes or file was truncated */
if (nsb.st_ino != sbp->st_ino) {
warnx("%s has been replaced, reopening.", fname);
if ((fp = freopen(fname, "r", fp)) == NULL) {
ierr();
if (kq >= 0)
close(kq);
return;
}
(void)memcpy(sbp, &nsb, sizeof(nsb));
goto kq_retry;
} else if ((queue && (ke.fflags & NOTE_TRUNCATE)) ||
(!queue && nsb.st_size < sbp->st_size)) {
warnx("%s has been truncated, resetting.", fname);
fpurge(fp);
rewind(fp);
}
(void)memcpy(sbp, &nsb, sizeof(nsb));
}
if (kq >= 0)
close(kq);
}
/*
* rlines -- display the last offset lines of the file.
*/
static int
rlines(FILE *fp, off_t off, struct stat *sbp)
{
off_t pos;
int ch;
pos = sbp->st_size;
if (pos == 0)
return (0);
/*
* Position before char.
* Last char is special, ignore it whether newline or not.
*/
pos -= 2;
ch = EOF;
for (; off > 0 && pos >= 0; pos--) {
/* A seek per char isn't a problem with a smart stdio */
if (fseeko(fp, pos, SEEK_SET) == -1) {
ierr();
return (1);
}
if ((ch = getc(fp)) == '\n')
off--;
else if (ch == EOF) {
if (ferror(fp)) {
ierr();
return (1);
}
break;
}
}
/* If we read until start of file, put back last read char */
if (pos < 0 && off > 0 && ch != EOF && ungetc(ch, fp) == EOF) {
ierr();
return (1);
}
while (!feof(fp) && (ch = getc(fp)) != EOF)
if (putchar(ch) == EOF)
oerr();
if (ferror(fp)) {
ierr();
return (1);
}
return (0);
}