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FILEMON(4) Device Drivers Manual FILEMON(4)

NAME

filemon —
the filemon device

SYNOPSIS

#include <dev/filemon/filemon.h>

DESCRIPTION

The filemon device allows a process to collect file operations data of its children. The device /dev/filemon responds to two ioctl(2) calls.
System calls are denoted using the following single letters:
‘C’
chdir(2)
‘D’
unlink(2)
‘E’
exec(2)
‘F’
fork(2), vfork(2)
‘L’
link(2), linkat(2), symlink(2), symlinkat(2)
‘M’
rename(2)
‘R’
open(2) for read
‘S’
stat(2)
‘W’
open(2) for write
‘X’
_exit(2)
Note that ‘R’ following ‘W’ records can represent a single open(2) for R/W, or two separate open(2) calls, one for ‘R’ and one for ‘W’. Note that only successful system calls are captured.

IOCTLS

User mode programs communicate with the filemon driver through a number of ioctls which are described below. Each takes a single argument.
Write the internal tracing buffer to the supplied open file descriptor.
Child process ID to trace.

RETURN VALUES

The ioctl() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

FILES

/dev/filemon
 

EXAMPLES

#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(\"/dev/filemon\", 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); 
	} 
}
Creates a file named filemon.out and configures the filemon device to write the filemon buffer contents to it.

SEE ALSO

dtrace(1), ktrace(1), truss(1), ioctl(2)

HISTORY

A filemon device appeared in FreeBSD 9.1.
June 14, 2013 Debian