freebsd-dev/usr.bin/tail/forward.c
Pedro F. Giffuni 8a16b7a18f General further adoption of SPDX licensing ID tags.
Mainly focus on files that use BSD 3-Clause license.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.
2017-11-20 19:49:47 +00:00

426 lines
9.4 KiB
C

/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* 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.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#ifndef lint
static const char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93";
#endif
#include <sys/param.h>
#include <sys/mount.h>
#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 *, const char *fn, off_t, struct stat *);
static int show(file_info_t *);
static void set_events(file_info_t *files);
/* defines for inner loop actions */
#define USE_SLEEP 0
#define USE_KQUEUE 1
#define ADD_EVENTS 2
static struct kevent *ev;
static int action = USE_SLEEP;
static int kq;
static const file_info_t *last;
/*
* 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(FILE *fp, const char *fn, enum STYLE style, off_t off, struct stat *sbp)
{
int ch;
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(fn);
return;
}
} else while (off--)
if ((ch = getc(fp)) == EOF) {
if (ferror(fp)) {
ierr(fn);
return;
}
break;
}
break;
case FLINES:
if (off == 0)
break;
for (;;) {
if ((ch = getc(fp)) == EOF) {
if (ferror(fp)) {
ierr(fn);
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(fn);
return;
}
} else if (off == 0) {
while (getc(fp) != EOF);
if (ferror(fp)) {
ierr(fn);
return;
}
} else
if (bytes(fp, fn, off))
return;
break;
case RLINES:
if (S_ISREG(sbp->st_mode))
if (!off) {
if (fseeko(fp, (off_t)0, SEEK_END) == -1) {
ierr(fn);
return;
}
} else
rlines(fp, fn, off, sbp);
else if (off == 0) {
while (getc(fp) != EOF);
if (ferror(fp)) {
ierr(fn);
return;
}
} else
if (lines(fp, fn, off))
return;
break;
default:
break;
}
while ((ch = getc(fp)) != EOF)
if (putchar(ch) == EOF)
oerr();
if (ferror(fp)) {
ierr(fn);
return;
}
(void)fflush(stdout);
}
/*
* rlines -- display the last offset lines of the file.
*/
static void
rlines(FILE *fp, const char *fn, 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(fn);
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(fn);
exit(1);
}
/* Set the file pointer to reflect the length displayed. */
if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) {
ierr(fn);
return;
}
if (map.start != NULL && munmap(map.start, map.maplen)) {
ierr(fn);
return;
}
}
static int
show(file_info_t *file)
{
int ch;
while ((ch = getc(file->fp)) != EOF) {
if (last != file && no_files > 1) {
if (!qflag)
printfn(file->file_name, 1);
last = file;
}
if (putchar(ch) == EOF)
oerr();
}
(void)fflush(stdout);
if (ferror(file->fp)) {
fclose(file->fp);
file->fp = NULL;
ierr(file->file_name);
return 0;
}
clearerr(file->fp);
return 1;
}
static void
set_events(file_info_t *files)
{
int i, n = 0;
file_info_t *file;
struct timespec ts;
struct statfs sf;
ts.tv_sec = 0;
ts.tv_nsec = 0;
action = USE_KQUEUE;
for (i = 0, file = files; i < no_files; i++, file++) {
if (! file->fp)
continue;
if (fstatfs(fileno(file->fp), &sf) == 0 &&
(sf.f_flags & MNT_LOCAL) == 0) {
action = USE_SLEEP;
return;
}
if (Fflag && fileno(file->fp) != STDIN_FILENO) {
EV_SET(&ev[n], fileno(file->fp), EVFILT_VNODE,
EV_ADD | EV_ENABLE | EV_CLEAR,
NOTE_DELETE | NOTE_RENAME, 0, 0);
n++;
}
EV_SET(&ev[n], fileno(file->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;
}
}
/*
* follow -- display the file, from an offset, forward.
*
*/
void
follow(file_info_t *files, enum STYLE style, off_t off)
{
int active, ev_change, i, n = -1;
struct stat sb2;
file_info_t *file;
struct timespec ts;
/* Position each of the files */
file = files;
active = 0;
n = 0;
for (i = 0; i < no_files; i++, file++) {
if (file->fp) {
active = 1;
n++;
if (no_files > 1 && !qflag)
printfn(file->file_name, 1);
forward(file->fp, file->file_name, style, off, &file->st);
if (Fflag && fileno(file->fp) != STDIN_FILENO)
n++;
}
}
if (!Fflag && !active)
return;
last = --file;
kq = kqueue();
if (kq < 0)
err(1, "kqueue");
ev = malloc(n * sizeof(struct kevent));
if (! ev)
err(1, "Couldn't allocate memory for kevents.");
set_events(files);
for (;;) {
ev_change = 0;
if (Fflag) {
for (i = 0, file = files; i < no_files; i++, file++) {
if (!file->fp) {
file->fp = fopen(file->file_name, "r");
if (file->fp != NULL &&
fstat(fileno(file->fp), &file->st)
== -1) {
fclose(file->fp);
file->fp = NULL;
}
if (file->fp != NULL)
ev_change++;
continue;
}
if (fileno(file->fp) == STDIN_FILENO)
continue;
if (stat(file->file_name, &sb2) == -1) {
if (errno != ENOENT)
ierr(file->file_name);
show(file);
if (file->fp != NULL) {
fclose(file->fp);
file->fp = NULL;
}
ev_change++;
continue;
}
if (sb2.st_ino != file->st.st_ino ||
sb2.st_dev != file->st.st_dev ||
sb2.st_nlink == 0) {
show(file);
file->fp = freopen(file->file_name, "r",
file->fp);
if (file->fp != NULL)
memcpy(&file->st, &sb2,
sizeof(struct stat));
else if (errno != ENOENT)
ierr(file->file_name);
ev_change++;
}
}
}
for (i = 0, file = files; i < no_files; i++, file++)
if (file->fp && !show(file))
ev_change++;
if (ev_change)
set_events(files);
switch (action) {
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 (lseek(ev->ident, (off_t)0, SEEK_END) == -1) {
ierr(file->file_name);
continue;
}
}
break;
case USE_SLEEP:
(void) usleep(250000);
break;
}
}
}