fs_usage man page on Darwin

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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] [-b] [-t seconds] [-R rawfile [-S
	      start_time] [-E end_time]] [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 running
     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 for‐
     matting 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 com‐
	     mands 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.  Multiple filtering options can be specified.  By
	     default, no output filtering occurs.  The supported modes are:

	     network	Network-related events are displayed.

	     filesys	Filesystem-related events are displayed.

	     pathname	Pathname-related events are displayed.

	     exec	Exec and spawn events are displayed.

	     diskio	Disk I/O events are displayed.

	     cachehit	In addition, show cache hits.

     -b	     Specifying the -b option annotates disk I/O events with BootCache
	     info (if available).

     -t seconds
	     Specifies a run timeout in seconds.  fs_usage will run for no
	     longer than the timeout specified.

     -R raw_file
	     Specifies a raw trace file to process.

     -S start_time
	     If -R is selected, specifies the start time in microseconds to
	     begin processing entries from the raw trace file. Entries with
	     timestamps before the specified start time will be skipped.

     -E end_time
	     If -R is selected, specifies the ending time in microseconds to
	     stop processing entries from the raw trace file.  Entries with
	     timestamps beyond the specified ending time will be skipped.

     pid | cmd
	     The sampled data can be limited to a list of process IDs or com‐
	     mands.  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, including 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 microsecond granu‐
	     larity.

     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.  Wide mode will append the
	     thread id to the process name (i.e Mail.nnn).

SAMPLE USAGE
     fs_usage -w -f filesys Mail

     fs_usage will display file system related data for all instances of pro‐
     cesses named Mail.	 Maximum data output will be displayed in the window.

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

Mac OS X		       November 7, 2002			      Mac OS X
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