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.Dd May 12, 2010
.Dt IOPRIO_GET 2
.Os
.Sh NAME
.Nm ioprio_get ,
.Nm ioprio_set
.Nd get/set the I/O priority
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/resource.h
.Ft int
.Fn ioprio_get "int which" "int who"
.Ft int
.Fn ioprio_set "int which" "int who" "int prio"
.Sh DESCRIPTION
The
.Fn ioprio_get
and
.Fn ioprio_set
functions get and set the I/O scheduler priority of a process, process group
or all processes of a user.
.Pp
The
.Fa which
argument specifies what type of resource's priority is to be modified.
It can have the following values (as defined in
.In sys/resource.h ) :
.Bl -tag -width ".Dv PRIO_PROCESS"
.It Dv PRIO_PROCESS
A single process
.It Dv PRIO_PGRP
A process group
.It Dv PRIO_USER
All processes of a user
.El
.Pp
The
.Fa who
argument specifies, depending on the
.Fa which
argument, either the process ID (if
.Fa which
is
.Dv PRIO_PROCESS ) ,
the process group ID (if
.Fa which
is
.Dv PRIO_PGRP ) ,
or the user ID (if
.Fa which
is
.Dv PRIO_USER ) .
A value of 0 specifies either the current process, the current process group,
or the current user.
.Pp
For the
.Fn ioprio_set
function, the
.Fa prio
argument specifies the priority to be set.
It can range from 1 to 10, with higher numbers indicating a higher priority.
.Sh RETURN VALUES
.Rv -std ioprio_get ioprio_set
.Sh ERRORS
The
.Fn ioprio_get
function will fail if:
.Bl -tag -width ".Bq Er EINVAL"
.It Bq Er EINVAL
An invalid value was specified for the
.Fa which
argument
.It Bq Er ESRCH
No corresponding process, process group or user could be found for the ID
specified in
.Fa who
.El
.Pp
The
.Fn ioprio_set
function will fail if:
.Bl -tag -width ".Bq Er EACCES"
.It Bq Er EACCES
The caller isn't allowed to access the I/O priority
.It Bq Er EINVAL
An invalid value was specified for the
.Fa which
argument
.It Bq Er EPERM
The caller doesn't own the specified process or processes
.It Bq Er ESRCH
No corresponding process, process group or user could be found for the ID
specified in
.Fa who
.El
.Sh SEE ALSO
.Xr ioprio 1
.Sh HISTORY
The
.Fn ioprio_get
and
.Fn ioprio_set
function calls first appeared in
.Dx 2.7 .
.Sh AUTHORS
.An -nosplit
.An Alex Hornung