IOSTAT(8)                   System Manager's Manual                  IOSTAT(8)

NAME
     iostat - report I/O statistics

SYNOPSIS
     iostat [-CdDIT] [-c count] [-M core] [-N system] [-w wait] [drives]

DESCRIPTION
     Iostat displays kernel I/O statistics on terminal, disk and cpu opera-
     tions.  By default, iostat displays one line of statistics averaged over
     the machine's run time.  The use of -c presents successive lines averaged
     over the wait period.  The -I option causes iostat to print raw, unaver-
     aged values.

     The options are as follows:

     -c    Repeat the display count times.  Unless the -I flag is in effect,
           the first display is for the time since a reboot and each subse-
           quent report is for the time period since the last display.  If no
           wait interval is specified, the default is 1 second.

     -C    Show cpu statistics.  This is enabled by default unless the -d, -D,
           or -T flags are used.

     -d    Show disk statistics.  This is the default.  Displays kilobytes per
           transfer, number of transfers, and megabytes transfered.  Use of
           this flag disables display of cpu and tty statistics.

     -D    Show alternate disk statistics.  Displays kilobytes transfered,
           number of transfers, and time spent in transfers.  Use of this flag
           disables the default display.

     -I    Show the running total values, rather than an average.

     -M    Extract values associated with the name list from the specified
           core instead of the default ``/dev/mem''.

     -N    Extract the name list from the specified system instead of the
           default ``/bsd''.

     -T    Show tty statistics.  This is enabled by default unless the -C, -d,
           or -D flags are used.

     -w    Pause wait seconds between each display.  If no repeat count is
           specified, the default is infinity.

     Iostat displays its information in the following format:

     tty
           tin     characters read from terminals
           tout    characters written to terminals

     disks
           Disk operations.  The header of the field is the disk name and unit
           number.  If more than four disk drives are configured in the sys-
           tem, iostat displays only the first four drives.  To force iostat
           to display specific drives, their names may be supplied on the com-
           mand line.

           KB/t    Kilobytes transferred per disk transfer
           t/s     transfers per second
           MB/s    Megabytes transferred per second

           The alternate display format, (selected with -D ), presents the
           following values.
           KB      Kilobytes transferred
           xfr     Disk transfers
           time    Seconds spent in disk activity

     cpu
           us      % of cpu time in user mode
           ni      % of cpu time in user mode running niced processes
           sy      % of cpu time in system mode
           in      % of cpu time processing interrupts
           id      % of cpu time in idle mode

FILES
     /bsd      Default kernel namelist.
     /dev/mem  Default memory file.

SEE ALSO
     fstat(1), netstat(1), nfsstat(1), ps(1), systat(1), pstat(8), vmstat(8)

     The sections starting with ``Interpreting system activity'' in Installing
     and Operating 4.3BSD.

BSD                              Jan 18, 1996                              BSD