freebsd-skq/share/man/man4/filemon.4
Sergey Kandaurov 0ec5ac100c Fix and improve filemon(4) example:
- remove return statements from void function [1]
- include missing header
- use O_CLOEXEC instead of separate fcntl() calls

PR:		docs/179459 [1]
MFC after:	1 week
2013-06-14 08:28:08 +00:00

175 lines
4.3 KiB
Groff

.\" Copyright (c) 2012
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.\" $FreeBSD$
.\"
.Dd June 14, 2013
.Dt FILEMON 4
.Os
.Sh NAME
.Nm filemon
.Nd the filemon device
.Sh SYNOPSIS
.In dev/filemon/filemon.h
.Sh DESCRIPTION
The
.Nm
device allows a process to collect file operations data of its children.
The device
.Pa /dev/filemon
responds to two
.Xr ioctl 2
calls.
.Pp
System calls are denoted using the following single letters:
.Pp
.Bl -tag -width indent -compact
.It Ql C
.Xr chdir 2
.It Ql D
.Xr unlink 2
.It Ql E
.Xr exec 2
.It Ql F
.Xr fork 2 ,
.Xr vfork 2
.It Ql L
.Xr link 2 ,
.Xr linkat 2 ,
.Xr symlink 2 ,
.Xr symlinkat 2
.It Ql M
.Xr rename 2
.It Ql R
.Xr open 2
for read
.It Ql S
.Xr stat 2
.It Ql W
.Xr open 2
for write
.It Ql X
.Xr _exit 2
.El
.Pp
Note that
.Ql R
following
.Ql W
records can represent a single
.Xr open 2
for R/W,
or two separate
.Xr open 2
calls, one for
.Ql R
and one for
.Ql W .
Note that only successful system calls are captured.
.Sh IOCTLS
User mode programs communicate with the
.Nm
driver through a number of ioctls which are described below.
Each takes a single argument.
.Bl -tag -width ".Dv FILEMON_SET_PID"
.It Dv FILEMON_SET_FD
Write the internal tracing buffer to the supplied open file descriptor.
.It Dv FILEMON_SET_PID
Child process ID to trace.
.El
.Sh RETURN VALUES
.\" .Rv -std ioctl
The
.Fn ioctl
function returns the value 0 if successful;
otherwise the value \-1 is returned and the global variable
.Va errno
is set to indicate the error.
.Sh FILES
.Bl -tag -width ".Pa /dev/filemon"
.It Pa /dev/filemon
.El
.Sh EXAMPLES
.Bd -literal
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/ioctl.h>
#include <dev/filemon/filemon.h>
#include <fcntl.h>
#include <err.h>
#include <unistd.h>
static void
open_filemon(void)
{
pid_t child;
int fm_fd, fm_log;
if ((fm_fd = open("/dev/filemon", O_RDWR | O_CLOEXEC)) == -1)
err(1, "open(\e"/dev/filemon\e", O_RDWR)");
if ((fm_log = open("filemon.out",
O_CREAT | O_WRONLY | O_TRUNC | O_CLOEXEC, DEFFILEMODE)) == -1)
err(1, "open(filemon.out)");
if (ioctl(fm_fd, FILEMON_SET_FD, &fm_log) == -1)
err(1, "Cannot set filemon log file descriptor");
if ((child = fork()) == 0) {
child = getpid();
if (ioctl(fm_fd, FILEMON_SET_PID, &child) == -1)
err(1, "Cannot set filemon PID");
/* Do something here. */
} else {
wait(&child);
close(fm_fd);
}
}
.Ed
.Pp
Creates a file named
.Pa filemon.out
and configures the
.Nm
device to write the
.Nm
buffer contents to it.
.Sh SEE ALSO
.Xr dtrace 1 ,
.Xr ktrace 1 ,
.Xr truss 1 ,
.Xr ioctl 2
.Sh HISTORY
A
.Nm
device appeared in
.Fx 9.1 .