.TH sg_get_disk_io_stats 3 $Date:\ 2005/04/25\ 11:25:45\ $ i\-scream 
.SH NAME
sg_get_disk_io_stats, sg_get_disk_io_stats_diff \- get disk io statistics
.SH SYNOPSIS
.nf
#include <statgrab.h>
.fi
.sp 1
.PP
sg_disk_io_stats *\fIsg_get_disk_io_stats\fR(int *\fIentries\fR);
.PP
sg_disk_io_stats *\fIsg_get_disk_io_stats_diff\fR(int *\fIentries\fR);
.SH DESCRIPTION
Both calls take a pointer to an int,
entries, which is filled with the number
of disks the machine has. This is needed to know how many
sg_disk_io_stats structures have been
returned. A pointer is returned to the first
sg_disk_io_stats.
.PP
sg_get_disk_io_stats returns the disk IO stored
in the kernel which holds the amount of data transferred since
bootup. On some platforms, such as Solaris 7, this value is
stored in a 32bit int, so wraps around when it reaches 4GB. Other
platforms, such as Solaris 8, hold the value in a 64bit int,
which wraps somewhere near 17 million terabytes.
.PP
sg_get_disk_io_stats_diff is the same as
sg_get_disk_io_stats except it will return the
difference since the last call. So, for instance a call to
sg_get_disk_io_stats_diff is made, and called
again 5 seconds later. Over that time, 2000 bytes of traffic were
written and 10000 bytes read. write_bytes
will store 2000 bytes, read_bytes will
store 10000, and systime will store 5.
This function copes with wrap arounds by the O/S so should be
seemless to use.
.PP
On Solaris libstatgrab will attempt to get the cXtXdXsX
representation for the disk_name string. If
it fails it will use a name like sd0. On some systems programs
calling libstatgrab will need elevated privileges to lookup
some of the names. The mappings are built up when
sg_init is called.
.SH RETURN\ VALUES
All diskio statistics return a pointer to a structure of type
sg_disk_io_stats.
.PP
.nf

typedef struct{
        char *disk_name;
        long long read_bytes;
        long long write_bytes;
        time_t systime;
}sg_disk_io_stats;
    
.fi
.TP 
disk_name  
The name known to the operating system.
(eg. on linux it might be hda)
.TP 
read_bytes  
The number of bytes the disk has read.
.TP 
write_bytes  
The number of bytes the disk has written.
.TP 
systime  
The time period over which read_bytes
and write_bytes were transferred.
.SH BUGS
On the very first call sg_get_disk_io_stats_diff
will return the same as sg_get_disk_io_stats.
After the first call it will always return the difference.
.PP
On operating systems that hold only 32bits of data there is a
problem if the values wrap twice. For example, on Solaris 7 if
9GB is transferred and the operating system wraps at 4GB, the
sg_get_disk_io_stats_diff function will return
5GB.
.SH SEE\ ALSO
\fBstatgrab\fR(3)
.SH WEBSITE
http://www.i\-scream.org/libstatgrab/