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NAMEgetpriority setpriority - get/set program scheduling priority
SYNOPSISIn sys/time.h In sys/resource.h Ft int Fn getpriority int which int who Ft int Fn setpriority int which int who int prio
DESCRIPTIONThe scheduling priority of the process, process group, or user, as indicated by Fa which and Fa who is obtained with the Fn getpriority system call and set with the Fn setpriority system call. The Fa which argument is one of PRIO_PROCESS PRIO_PGRP or PRIO_USER and Fa who is interpreted relative to Fa which (a process identifier for PRIO_PROCESS process group identifier for PRIO_PGRP and a user ID for PRIO_USER ) A zero value of Fa who denotes the current process, process group, or user. The Fa prio argument is a value in the range -20 to 20. The default priority is 0; lower priorities cause more favorable scheduling.
The Fn getpriority system call returns the highest priority (lowest numerical value) enjoyed by any of the specified processes. The Fn setpriority system call sets the priorities of all of the specified processes to the specified value. Only the super-user may lower priorities.
RETURN VALUESSince Fn getpriority can legitimately return the value -1, it is necessary to clear the external variable errno prior to the call, then check it afterward to determine if a -1 is an error or a legitimate value.
Rv -std setpriority
ERRORSThe Fn getpriority and Fn setpriority system calls will fail if:
- Bq Er ESRCH
- No process was located using the Fa which and Fa who values specified.
- Bq Er EINVAL
- The Fa which argument was not one of PRIO_PROCESS PRIO_PGRP or PRIO_USER
In addition to the errors indicated above, Fn setpriority will fail if:
- Bq Er EPERM
- A process was located, but neither its effective nor real user ID matched the effective user ID of the caller.
- Bq Er EACCES
- A non super-user attempted to lower a process priority.