## NAME

chrt - manipulate the real-time attributes of a process

## SYNOPSIS

chrt

command\ [ arg ]...
chrt

-p

## DESCRIPTION

chrt sets or retrieves the real-time scheduling attributes of an existing pid, or runs command with the given attributes. Both policy (one of SCHED_OTHER, SCHED_FIFO, SCHED_RR, SCHED_BATCHor SCHED_IDLE )and priority can be set and retrieved.

The SCHED_BATCHpolicy is supported since Linux 2.6.16. The SCHED_IDLEpolicy is supported since Linux 2.6.23.

The SCHED_RESET_ON_FORKflag for policies SCHED_RR and SCHED_FIFO is supported since Linux 2.6.31.

## OPTIONS

-a, --all-tasks Set or retrieve the scheduling attributes of all the tasks (threads) for a given PID.

-b, --batch Set scheduling policy to , SCHED_BATCH(Linux specific).

-f, --fifo Set scheduling policy to SCHED_FIFO .

-i, --idle Set scheduling policy to SCHED_IDLE(Linux specific).

-m, --max Show minimum and maximum valid priorities, then exit.

-o, --other Set policy scheduling policy to SCHED_OTHER .

-p, --pid Operate on an existing PID and do not launch a new task.

-r, --rr Set scheduling policy to SCHED_RR .When policy is not defined the SCHED_RR is used as default.

-R, --reset-on-fork Add SCHED_RESET_ON_FORK flag to the SCHED_FIFO or SCHED_RR scheduling policy (Linux specific).

-v, --verbose Show status information.

-h, --help Display help text and exit.

-V, --version Display version information and exit.

## USAGE

The default behavior is to run a new command: chrt prio command\ [ arguments ]

You can also retrieve the real-time attributes of an existing task: chrt -p pid

Or set them: chrt -r -p prio pid

## PERMISSIONS

A user must possess CAP_SYS_NICEto change the scheduling attributes of a process. Any user can retrieve the scheduling information.

## NOTES

Only SCHED_FIFO, SCHED_OTHERand SCHED_RRare part of POSIX 1003.1b Process Scheduling. The other scheduling attributes may be ignored on some systems.

Linux default scheduling policy is SCHED_OTHER .

## AUTHOR

Written by Robert M. Love.

## COPYRIGHT

Copyright © 2004 Robert M. Love
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

## SEE ALSO

taskset (1), nice (1), renice (1)

See sched_setscheduler (2)for a description of the Linux scheduling scheme.

## AVAILABILITY

The chrt command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.