.\" Copyright (c) 2000, Apple Computer, Inc.  All rights reserved.
.\"
.Dd November 7, 2002
.Dt FS_USAGE 1
.Os "Mac OS X"
.Sh NAME
.Nm fs_usage
.Nd report system calls and page faults related to filesystem activity in
real-time
.Sh SYNOPSIS
.Nm fs_usage [-e] [-w] [-f mode] [-b] [-t seconds] [-R rawfile [-S start_time] [-E end_time]] [pid | cmd [pid | cmd] ...]
.Sh DESCRIPTION
The
.Nm fs_usage
utility presents an ongoing display of system call usage information
pertaining to filesystem activity.
It requires root privileges due to the kernel tracing facility it uses to
operate.
By default, the activity monitored includes all system processes except the
running
.Nm fs_usage
process, Terminal, telnetd, telnet, sshd, rlogind, tcsh, csh, sh, and zsh.
These defaults can be overridden such that output is limited to include or
exclude a list of processes specified by the user.
.Pp
The output presented by
.Nm 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
.Fl w
option.
In this case, the data displayed will wrap
when the window is not wide enough.
.Pp
The options are as follows:
.Bl -tag -width Ds
.\" ==========
.It Fl e
Specifying the
.Fl 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.
.\" ==========
.It Fl w
Specifying the
.Fl w
option forces a wider, more detailed output,
regardless of the window size.
.\" ==========
.It Fl f
Specifying the
.Fl f
option turns on output filtering based on the
.Pa mode
provided.
Multiple filtering options can be specified.
By default, no output filtering occurs.
The supported modes are:
.Pp
.Pa  network	
Network-related events are displayed.
.Pp
.Pa filesys	
Filesystem-related events are displayed.
.Pp
.Pa pathname	
Pathname-related events are displayed.
.Pp
.Pa exec		
Exec and spawn events are displayed.
.Pp
.Pa diskio	
Disk I/O events are displayed.
.Pp
.Pa cachehit	
In addition, show cache hits.
.\" ==========
.It Fl b
Specifying the
.Fl b
option annotates disk I/O events with BootCache info (if available).
.\" ==========
.It Fl t Ar seconds
Specifies a run timeout in seconds.  
.Nm fs_usage
will run for no longer than the timeout specified.
.\" ==========
.It Fl R Ar raw_file
Specifies a raw trace file to process.
.\" ==========
.It Fl S Ar start_time
If 
.Fl 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.
.\" ==========
.It Fl E Ar end_time
If 
.Fl 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.
.\" ==========
.It  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
.Fl e
option has the opposite effect,
excluding sampled data relating to the given list
of process IDs or commands.
.El
.Pp
The data columns displayed are as follows:
.Bl -tag -width Ds
.Pp
.It TIMESTAMP
TOD when call occurred.
Wide mode will have microsecond granularity.
.It CALL
The name of the network or filesystem related call, page-in, page-out,
or physical disk access.
.It 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.
.It BYTE COUNT
Of the form B=x, x is the number of bytes requested by the call.
.It [ERRNO]
On error, the errno is displayed in brackets.
.It PATHNAME
Pathname of the file accessed (up to the last 28 bytes).
.It FAULT ADDRESS
Of the form A=0xnnnnnnnn,
where 0xnnnnnnnn is the address being faulted.
.It DISK BLOCK NUMBER
Of the form D=0xnnnnnnnn,
where 0xnnnnnnnn is the block number
of the physical disk block being read or written.
.It OFFSET    
Of the form O=0xnnnnnnnn, where 0xnnnnnnnn is a file offset.
.It 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.
.It TIME INTERVAL(W)
The elapsed time spent in the system call.
A 
.Sq Li 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.
.It PROCESS NAME
The process that made the system call.  Wide mode will append the
thread id to the process name (i.e Mail.nnn).
.El
.Pp
.Sh SAMPLE USAGE
.Pp
fs_usage -w -f filesys Mail
.Pp
.Nm fs_usage
will display file system related data
for all instances of processes named Mail.
Maximum data output will be displayed in the window.
.Sh SEE ALSO
.Xr dyld 1 ,
.Xr latency 1 ,
.Xr sc_usage 1 ,
.Xr top 1