The renice command alters the scheduling priority of one or more running processes. By default, the processes to be affected are specified by their process IDs.
If the first operand is a number within the valid range of priorities (-20 to 20), renice will treat it as a priority (as in all but the first synopsis form). Otherwise, renice will treat it as an ID (as in the first synopsis form).
Users other than the privileged user may only alter the priority of processes they own, and can only monotonically increase their “nice value” within the range 0 to 19. This prevents overriding administrative fiats. The privileged user may alter the priority of any process and set the priority to any value in the range -20 to 19. Useful priorities are: 19 (the affected processes will run only when nothing else in the system wants to); 0 (the “base” scheduling priority),; and any negative value (to make things go very fast). 20 is an acceptable nice value, but will be rounded down to 19.
renice supports the following option features:
The first operand, priority, must precede the options and can have the appearance of a multi-digit option.
The -g, -p, and -u options can each take multiple option-arguments.
The pid option-argument can be used without its -p option.
The -i option can be used to specify the ID type for the ID list. This is preferred in specifying ID type over the use of the -g | -p | -u syntax, which is now obsolete. See NOTES.
The following options are supported:
Interprets all operands or just the gid arguments as unsigned decimal integer process group IDs.
This option, together with the ID list arguments, specifies a class of processes to which the renice command is to apply. The interpretation of the ID list depends on the value of idtype. The valid idtype arguments are: pid, pgid, uid, gid, sid, taskid, and projid.
Specifies how the system scheduling priority of the specified process or processes is to be adjusted. The increment option-argument is a positive or negative decimal integer that will be used to modify the system scheduling priority of the specified process or processes. Positive increment values cause a lower system scheduling priority. Negative increment values may require appropriate privileges and will cause a higher system scheduling priority.
Interprets all operands or just the pid arguments as unsigned decimal integer process IDs. The -p option is the default if no options are specified.
Interprets all operands or just the user argument as users. If a user exists with a user name equal to the operand, then the user ID of that user will be used in further processing. Otherwise, if the operand represents an unsigned decimal integer, it will be used as the numeric user ID of the user.
The following operands are supported:
A process ID, process group ID or user name/user ID, depending on the option selected.
The value specified is taken as the actual system scheduling priority, rather than as an increment to the existing system scheduling priority. Specifying a scheduling priority higher than that of the existing process may require appropriate privileges.
Adjust the system scheduling priority so that process IDs 987 and 32 would have a lower scheduling priority:
example% renice -n 5 -p 987 32
Adjust the system scheduling priority so that group IDs 324 and 76 would have a higher scheduling priority, if the user has the appropriate privileges to do so:
example% renice -n -4 -g 324 76
Adjust the system scheduling priority so that numeric user ID 8 and user sas would have a lower scheduling priority:
example% renice -n 4 -u 8 sas
See environ(5) for descriptions of the following environment variables that affect the execution of renice: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, and NLSPATH.
See attributes(5) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
The renice syntax
renice [-n increment] [-i idtype] ID ...
is preferred over the old syntax
renice [-n increment] [-g | -p| -u] ID ...
which is now obsolete.
If you make the priority very negative, then the process cannot be interrupted.
To regain control you must make the priority greater than 0.
Users other than the privileged user cannot increase scheduling priorities of their own processes, even if they were the ones that decreased the priorities in the first place.
The priocntl command subsumes the function of renice.