xref: /freebsd/share/man/man4/filemon.4 (revision f5f7c05209ca2c3748fd8b27c5e80ffad49120eb)
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2.\"	David E. O'Brien <obrien@FreeBSD.org>.  All rights reserved.
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32.\" $FreeBSD$
33.\"
34.Dd May 30, 2012
35.Dt FILEMON 4
36.Os
37.Sh NAME
38.Nm filemon
39.Nd the filemon device
40.Sh SYNOPSIS
41.In dev/filemon/filemon.h
42.Sh DESCRIPTION
43The
44.Nm
45device allows a process to collect file operations data of its children.
46The device
47.Pa /dev/filemon
48responds to two
49.Xr ioctl 2
50calls.
51.Pp
52System calls are denoted using the following single letters:
53.Pp
54.Bl -tag -width indent -compact
55.It Ql C
56.Xr chdir 2
57.It Ql D
58.Xr unlink 2
59.It Ql E
60.Xr exec 2
61.It Ql F
62.Xr fork 2 ,
63.Xr vfork 2
64.It Ql L
65.Xr link 2 ,
66.Xr linkat 2 ,
67.Xr symlink 2 ,
68.Xr symlinkat 2
69.It Ql M
70.Xr rename 2
71.It Ql R
72.Xr open 2
73for read
74.It Ql S
75.Xr stat 2
76.It Ql W
77.Xr open 2
78for write
79.It Ql X
80.Xr _exit 2
81.El
82.Pp
83Note that
84.Ql R
85following
86.Ql W
87records can represent a single
88.Xr open 2
89for R/W,
90or two separate
91.Xr open 2
92calls, one for
93.Ql R
94and one for
95.Ql W .
96Note that only successful system calls are captured.
97.Sh IOCTLS
98User mode programs communicate with the
99.Nm
100driver through a number of ioctls which are described below.
101Each takes a single argument.
102.Bl -tag -width ".Dv FILEMON_SET_PID"
103.It Dv FILEMON_SET_FD
104Write the internal tracing buffer to the supplied open file descriptor.
105.It Dv FILEMON_SET_PID
106Child process ID to trace.
107.El
108.Sh RETURN VALUES
109.\" .Rv -std ioctl
110The
111.Fn ioctl
112function returns the value 0 if successful;
113otherwise the value \-1 is returned and the global variable
114.Va errno
115is set to indicate the error.
116.Sh FILES
117.Bl -tag -width ".Pa /dev/filemon"
118.It Pa /dev/filemon
119.El
120.Sh EXAMPLES
121.Bd -literal
122#include <sys/types.h>
123#include <sys/stat.h>
124#include <sys/wait.h>
125#include <sys/ioctl.h>
126#include <dev/filemon/filemon.h>
127#include <fcntl.h>
128#include <err.h>
129
130static void
131open_filemon(void)
132{
133	pid_t child;
134	int fm_fd, fm_log;
135
136	if ((fm_fd = open("/dev/filemon", O_RDWR)) == -1)
137		err(1, "open(\e"/dev/filemon\e", O_RDWR)");
138	if ((fm_log = open("filemon.out",
139	    O_CREAT | O_WRONLY | O_TRUNC, DEFFILEMODE)) == -1)
140		err(1, "open(filemon.out)");
141
142	if (ioctl(fm_fd, FILEMON_SET_FD, &fm_log) == -1)
143		err(1, "Cannot set filemon log file descriptor");
144	/* Set up these two fd's to close on exec. */
145	(void)fcntl(fm_fd, F_SETFD, FD_CLOEXEC);
146	(void)fcntl(fm_log, F_SETFD, FD_CLOEXEC);
147
148	if ((child = fork()) == 0) {
149		child = getpid();
150		if (ioctl(fm_fd, FILEMON_SET_PID, &child) == -1)
151			err(1, "Cannot set filemon PID");
152		/* Do something here. */
153		return 0;
154	} else {
155		wait(&child);
156		close(fm_fd);
157	}
158	return 0;
159}
160.Ed
161.Pp
162Creates a file named
163.Pa filemon.out
164and configures the
165.Nm
166device to write the
167.Nm
168buffer contents to it.
169.Sh SEE ALSO
170.Xr dtrace 1 ,
171.Xr ktrace 1 ,
172.Xr truss 1 ,
173.Xr ioctl 2
174.Sh HISTORY
175A
176.Nm
177device appeared in
178.Fx 9.1 .
179