290 lines
7.1 KiB
C
290 lines
7.1 KiB
C
/* $NetBSD: forward.c,v 1.16 1999/07/21 06:38:49 cgd Exp $ */
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/*-
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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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#include <sys/cdefs.h>
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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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__RCSID("$NetBSD: forward.c,v 1.16 1999/07/21 06:38:49 cgd Exp $");
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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 <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 "extern.h"
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static int rlines __P((FILE *, long, struct stat *));
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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;
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struct timeval second;
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int dostat = 0;
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struct stat statbuf;
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off_t lastsize = 0;
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dev_t lastdev;
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ino_t lastino;
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/* Keep track of file's previous incarnation. */
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lastdev = sbp->st_dev;
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lastino = sbp->st_ino;
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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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}
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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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if (rlines(fp, off, sbp))
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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 (lines(fp, off))
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return;
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}
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break;
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default:
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break;
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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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}
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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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/*
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* We pause for one second after displaying any data that has
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* accumulated since we read the file. Since sleep(3) takes
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* eight system calls, use select() instead.
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*/
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second.tv_sec = 1;
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second.tv_usec = 0;
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if (select(0, NULL, NULL, NULL, &second) == -1)
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err(1, "select: %s", strerror(errno));
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clearerr(fp);
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if (fflag == 1)
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continue;
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/*
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* We restat the original filename every five seconds. If
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* the size is ever smaller than the last time we read it,
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* the file has probably been truncated; if the inode or
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* or device number are different, it has been rotated.
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* This causes us to close it, reopen it, and continue
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* the tail -f. If stat returns an error (say, because
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* the file has been removed), just continue with what
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* we've got open now.
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*/
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if (dostat > 0) {
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dostat -= 1;
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} else {
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dostat = 5;
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if (stat(fname, &statbuf) == 0) {
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if (statbuf.st_dev != lastdev ||
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statbuf.st_ino != lastino ||
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statbuf.st_size < lastsize) {
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lastdev = statbuf.st_dev;
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lastino = statbuf.st_ino;
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lastsize = 0;
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fclose(fp);
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if ((fp = fopen(fname, "r")) == NULL)
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err(1, "can't reopen %s: %s",
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fname, strerror(errno));
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} else {
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lastsize = statbuf.st_size;
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}
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}
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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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* Non-zero return means than a (non-fatal) error occurred.
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*/
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static int
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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 (0);
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if (size > SIZE_T_MAX) {
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err(0, "%s: %s", fname, strerror(EFBIG));
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return (1);
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}
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if ((start = mmap(NULL, (size_t)size, PROT_READ,
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MAP_FILE|MAP_SHARED, fileno(fp), (off_t)0)) == (caddr_t)-1) {
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err(0, "%s: %s", fname, strerror(EFBIG));
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return (1);
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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 (1);
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}
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if (munmap(start, (size_t)sbp->st_size)) {
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err(0, "%s: %s", fname, strerror(errno));
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return (1);
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}
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return (0);
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}
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