CHRT(1)                                   User Commands                                   CHRT(1)



NAME
       chrt - manipulate the real-time attributes of a process

SYNOPSIS
       chrt [options] prio command [arg]...
       chrt [options] -p [prio] pid

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_BATCH, or SCHED_IDLE) and priority can be set and retrieved.

       The  SCHED_BATCH  policy  is  supported since Linux 2.6.16.  The SCHED_IDLE policy is sup‐
       ported since Linux 2.6.23.

       The SCHED_RESET_ON_FORK flag 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_NICE to change the scheduling attributes of  a  process.   Any
       user can retrieve the scheduling information.

NOTES
       Only  SCHED_FIFO,  SCHED_OTHER  and SCHED_RR are 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.ker‐
       nel.org/pub/linux/utils/util-linux/.



util-linux                                  June 2010                                     CHRT(1)