getpriority, setpriority - Gets or sets process scheduling priority
[Digital] The following declaration of the who parameter for getpriority() and setpriority() does not conform to current standards and is supported only for backward compatibility:
Interfaces documented on this reference page conform to industry standards as follows:
getpriority(), setpriority(): XPG4-UNIX
Refer to the standards(5) reference page for more information about industry standards and associated tags.
Specifies one of PRIO_PROCESS (process priority), PRIO_PGRP (process group priority), or PRIO_USER (user priority). Specifies a numeric value interpreted relative to the which parameter (a process identifier, process group identifier, and a user ID, respectively). A 0 (zero) value for the who parameter denotes the current process, process group, or user. Specifies a value in the range -20 to 20. The default priority is 0 (zero); negative priorities cause more favorable scheduling.
The getpriority() function obtains the current priority of a process, process group, or user. The getpriority() function returns the highest priority (lowest numerical value) pertaining to any of the specified processes.
The setpriority() function sets the scheduling priority of a process, process group, or user. If you specify more than one process, the setpriority() function sets the priorities of all of the specified processes to the specified value. If the specified value is less than -20, a value of -20 is used; if it is greater than 20, a value of 20 is used.
Upon successful completion, the getpriority() function returns an integer in the range -20 to 20. Otherwise, -1 is returned and errno is set to indicated the error.
Because 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.
Upon successful completion, the setpriority() function returns 0 (zero). Otherwise, the function returns -1 and sets errno to indicate the error.
The getpriority() and setpriority() functions set errno to the specified values for the following conditions: No process was located using the which and who parameter values specified. The which parameter was not recognized.
In addition to the errors indicated above, the setpriority() function can fail with errno set to one of the following values: The process does not have ownership rights with respect to the target process's real user ID. The process is trying to raise its priority and does not have the appropriate privilege.
Standards: standards(5) delim off