.\" 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] [ 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, 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.
.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.
By default no filtering occurs.
The supported modes are:
.Pp
.Pa  network	
Only network related output is displayed.
.Pp
.Pa filesys	
Only file system related output is displayed.
.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
If you set the DYLD_IMAGE_SUFFIX environment variable to
.Dq Li _debug ,
then an application will use the debug version of all libraries including the
Carbon FileManager.
See
.Xr dyld 1 .
When
.Nm 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.
.Pp
The data columns displayed are as follows:
.Bl -tag -width Ds
.Pp
.It TIMESTAMP
TOD when call occurred.
Wide mode will have millisecond 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.
.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 top 1 ,
.Xr sc_usage 1 ,
.Xr latency 1 ,
.Xr dyld 1