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Since kqueue support was added to tail, the "-F" option (check for

Browse Source 
renames/rotations) only detected cases where the file itself was
moved or deleted. If part of the path to the file (or a symlink
in the path) was changed instead, tail would not notice.

Fix this by ensuring that we stat the path at least once every
second in the -F case to check for changes. We still use kqueue
when possible to inform us quickly when the file has changed.

PR:		bin/24955
Submitted by:	Maxim Konovalov <maxim@macomnet.ru>
MFC after:	1 week
This commit is contained in:
Ian Dowse 2001-11-25 18:03:28 +00:00
parent 29921a60d7
commit aee1bac713
1 changed files with 34 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

64
usr.bin/tail/forward.c
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@ -94,10 +94,11 @@ forward(fp, style, off, sbp)
off_t off;
struct stat *sbp;
{
int ch, kq = -1;
int ch, n, kq = -1;
int action = USE_SLEEP;
struct kevent ev[2];
struct stat sb2;
struct timespec ts;
switch(style) {
case FBYTES:
@ -193,9 +194,10 @@ forward(fp, style, off, sbp)
clearerr(fp);
switch (action) {
case ADD_EVENTS: {
int n = 0;
struct timespec ts = { 0, 0 };
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,
@ -208,24 +210,27 @@ forward(fp, style, off, sbp)
n++;
if (kevent(kq, ev, n, NULL, 0, &ts) < 0) {
close(kq);
kq = -1;
action = USE_SLEEP;
} else {
action = USE_KQUEUE;
}
break;
}
case USE_KQUEUE:
if (kevent(kq, NULL, 0, ev, 1, NULL) < 0)
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 (ev->filter == EVFILT_VNODE) {
/* file was rotated, wait until it reappears */
action = USE_SLEEP;
} else if (ev->data < 0) {
/* file shrank, reposition to end */
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;
@ -236,26 +241,25 @@ forward(fp, style, off, sbp)
case USE_SLEEP:
(void) usleep(250000);
clearerr(fp);
break;
}
if (Fflag && fileno(fp) != STDIN_FILENO &&
stat(fname, &sb2) != -1) {
if (sb2.st_ino != sbp->st_ino ||
sb2.st_dev != sbp->st_dev ||
sb2.st_rdev != sbp->st_rdev ||
sb2.st_nlink == 0) {
fp = freopen(fname, "r", fp);
if (fp == NULL) {
ierr();
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_rdev != sbp->st_rdev ||
sb2.st_nlink == 0) {
fp = freopen(fname, "r", fp);
if (fp == NULL) {
ierr();
} else {
*sbp = sb2;
if (kq != -1)
action = ADD_EVENTS;
} else if (kq != -1) {
action = USE_KQUEUE;
action = ADD_EVENTS;
}
}
break;
}
}
}