.\" Copyright (c) 1985, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" %sccs.include.redist.roff%
.\"
.\"	@(#)iostat.8	8.1 (Berkeley) 06/06/93
.\"
.Dd 
.Dt IOSTAT 8
.Os BSD 4
.Sh NAME
.Nm iostat
.Nd report
.Tn I/O
statistics
.Sh SYNOPSIS
.Nm iostat
.Op Fl c Ar count
.Op Fl M Ar core
.Op Fl N Ar system
.Op Fl w Ar wait
.Op Ar drives
.Sh DESCRIPTION
.Nm Iostat
displays kernel
.Tn I/O
statistics on terminal, disk and cpu
operations.
.Pp
The options are as follows:
.Bl -tag -width flag
.It Fl c
Repeat the display
.Ar count
times.
The first display is for the time since a reboot and each subsequent
report is for the time period since the last display.
If no
.Ar wait
interval is specified, the default is 1 second.
.It Fl M
Extract values associated with the name list from the specified core
instead of the default
.Dq Pa /dev/kmem .
.It Fl N
Extract the name list from the specified system instead of the default
.Dq Pa /vmunix .
.It Fl w
Pause
.Ar wait
seconds between each display.
If no repeat
.Ar count
is specified, the default is infinity.
.El
.Pp
.Nm Iostat
displays its information in the following format:
.Bl -tag -width flag
.It tty
.Bl -tag -width indent -compact
.It tin
characters read from terminals
.It tout
characters written to terminals
.El
.It disks
Disk operations (this field is system dependent). 
The header of the field is the disk name and unit number.
If more than four disk drives are configured in the system,
.Nm iostat
displays only the first four drives.
To force
.Nm iostat
to display specific drives, their names may be supplied on the command
line.
.Pp
.Bl -tag -width indent -compact
.It sps
sectors transferred per second
.It tps
transfers per second
.It msps
milliseconds per average seek (including implied
seeks and rotational latency)
.El
.It cpu
.Bl -tag -width indent -compact
.It \&us
% of cpu time in user mode
.It \&ni
% of cpu time in user mode running niced processes
.It \&sy
% of cpu time in system mode
.It \&id
% of cpu time in idle mode
.El
.El
.Sh FILES
.Bl -tag -width /dev/kmem -compact
.It Pa /vmunix
Default kernel namelist.
.It Pa /dev/kmem
Default memory file.
.El
.Sh SEE ALSO
.Xr fstat 1 ,
.Xr netstat 1 ,
.Xr nfsstat 1 ,
.Xr \&ps 1 ,
.Xr systat 1 ,
.Xr vmstat 1 ,
.Xr pstat 8
.Pp
The sections starting with ``Interpreting system activity'' in
.%T "Installing and Operating 4.3BSD" .