FS_USAGE(1)						    BSD General Commands Manual 					       FS_USAGE(1)

NAME

     fs_usage -- report system calls and page faults related to filesystem activity in real-time

SYNOPSIS

     fs_usage [-e] [-w] [-f mode] [pid|cmd [pid|cmd] ...]

DESCRIPTION

     The fs_usage utility presents an ongoing display of system call usage information pertaining to filesystem activity.  It requires root privi-
     leges due to the kernel tracing facility it uses to operate.  By default the activity monitored includes all system processes except the run-
     ning fs_usage process, Terminal, telnetd, sshd, rlogind, tcsh, csh and sh.  These defaults can be overridden such that output is limited to
     include or exclude a list of processes specified by the user.

     The output presented by fs_usage is formatted according to the size of your window.  A narrow window will display fewer columns of data.  Use
     a wide window for maximum data display.  You may override the window formatting restrictions by forcing a wide display with the -w option.
     In this case, the data displayed will wrap when the window is not wide enough.

     The options are as follows:

     -e      Specifying the -e option generates output that excludes sampling of the running fs_usage tool.  If a list of process ids or commands
	     is also given, then those processes are also excluded from the sampled output.

     -w      Specifying the -w option forces a wider, more detailed output, regardless of the window size.

     -f      Specifying the -f option turns on output filtering based on the mode provided.  By default no filtering occurs.  The supported modes
	     are:

	     network	Only network related output is displayed.

	     filesys	Only file system related output is displayed.

     pid | cmd
	     The sampled data can be limited to a list of process ids or commands.  When a command name is given, all processes with that name
	     will be sampled.  Using the -e option has the opposite effect, excluding sampled data relating to the given list of process ids or
	     commands.

     If you set the DYLD_IMAGE_SUFFIX environment variable to ``_debug'', then an application will use the debug version of all libraries includ-
     ing the Carbon FileManager.  See dyld(1).	When fs_usage is run against a Carbon Application launched in this environment, then the high
     level Carbon FileManager calls will be displayed bracketing the system calls that they are built on.

     The data columns displayed are as follows:

     TIMESTAMP
	     TOD when call occurred.  Wide mode will have millisecond granularity.

     CALL    The name of the network or filesystem related call, page-in, page-out or physical disk access.

     FILE DESCRIPTOR
	     Of the form F=x, x is a file descriptor.  Depending on the type of system call, this will be either an input value or a return value.

     BYTE COUNT
	     Of the form B=x, x is the number of bytes requested by the call.

     [ERRNO]
	     On error, the errno is displayed in brackets.

     PATHNAME
	     Pathname of the file accessed (up to the last 28 bytes).

     FAULT ADDRESS
	     Of the form A=0xnnnnnnnn, where 0xnnnnnnnn is the address being faulted.

     DISK BLOCK NUMBER
	     Of the form D=0xnnnnnnnn, where 0xnnnnnnnn is the block number of the physical disk block being read or written.

     OFFSET  Of the form O=0xnnnnnnnn, where 0xnnnnnnnn is a file offset.

     SELECT RETURN
	     Of the form S=x, x is the number of ready descriptors returned by the select() system call.  If S=0, the time limit expired.

     TIME INTERVAL(W)
	     The elapsed time spent in the system call.  A 'W' after the elapsed time indicates the process was scheduled out during this file
	     activity.	In this case, the elapsed time includes the wait time.

     PROCESS NAME
	     The process that made the system call.

SAMPLE USAGE

     fs_usage -w -f filesys Mail

     fs_usage will display file system related data for all instances of processes named Mail.	Maximum data output will be displayed in the win-
     dow.

SEE ALSO

     top(1), sc_usage(1), latency(1), dyld(1)

Mac OS X							 November 7, 2002							  Mac OS X