.\" chrt(1) manpage
.\"
.\" Copyright (C) 2004 Robert Love
.\"
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.\" modify it under the terms of the GNU General Public License as
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
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.\" 2002-05-11 Robert Love <rml@tech9.net>
.\" 	Initial version
.\"
.TH CHRT "1" "Apr 2003" "schedutils" "Linux User's Manual"
.SH NAME
chrt \- manipulate real-time attributes of a process
.SH SYNOPSIS
.B chrt
.RI [ options ]\  prio
.IR command\  [ arg ]...
.br
.B chrt
.RI [ options ]
.B \-p
.RI [ prio ]\  pid
.SH DESCRIPTION
.PP
.BR chrt (1)
sets or retrieves the real-time scheduling attributes of an existing PID or
runs COMMAND with the given attributes.  Both policy (one of
.BR SCHED_OTHER ,
.BR SCHED_FIFO ,
.BR SCHED_RR ,
.BR SCHED_BATCH ,
or
.BR SCHED_IDLE )
and priority can be set and retrieved.
.PP
The
.BR SCHED_BATCH
policy is supported since Linux 2.6.16. The
.BR SCHED_IDLE
policy is supported since Linux 2.6.23.
.SH OPTIONS
.TP
.B -p, --pid
operate on an existing PID and do not launch a new task
.TP
.B -b, --batch
set scheduling policy to
.BR SCHED_BATCH
.TP
.B -f, --fifo
set scheduling policy to
.BR SCHED_FIFO
.TP
.B -i, --idle
set schedulng policy to
.BR SCHED_IDLE
.TP
.B -m, --max
show minimum and maximum valid priorities, then exit
.TP
.B -o, --other
set policy scheduling policy to
.BR SCHED_OTHER
.TP
.B -r, --rr
set scheduling policy to
.BR SCHED_RR
(the default)
.TP
.B -h, --help
display usage information and exit
.TP
.B -v, --version
output version information and exit
.SH USAGE
.TP
The default behavior is to run a new command::
chrt prio command [arguments]
.TP
You can also retrieve the real-time attributes of an existing task:
chrt -p pid
.TP
Or set them:
chrt -p prio pid
.SH PERMISSIONS
A user must possess
.BR CAP_SYS_NICE
to change the scheduling attributes of a process.  Any user can retrieve the
scheduling information.
.SH AUTHOR
Written by Robert M. Love.
.SH COPYRIGHT
Copyright \(co 2004 Robert M. Love
.br
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
.SH "SEE ALSO"
.BR taskset (1),
.BR nice (1),
.BR renice (1)
.sp
See
.BR sched_setscheduler (2)
for a description of the Linux scheduling scheme.
.SH AVAILABILITY
The chrt command is part of the util-linux-ng package and is available from
ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.