getpriority, setpriority - Gets or sets process scheduling priority
[Tru64 UNIX] The following declaration of the who parameter for getprior-
ity() and setpriority() does not conform to current standards and is sup-
ported only for backward compatibility:
Interfaces documented on this reference page conform to industry standards
getpriority(), setpriority(): XSH4.2
Refer to the standards(5) reference page for more information about indus-
try standards and associated tags.
which Specifies one of PRIO_PROCESS (process priority), PRIO_PGRP (pro-
cess group priority), or PRIO_USER (user priority).
who 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.
priority 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, pro-
cess group, or user. The getpriority() function returns the highest prior-
ity (lowest numerical value) pertaining to any of the specified processes.
The setpriority() function sets the scheduling priority of a process, pro-
cess group, or user. If you specify more than one process, the setprior-
ity() 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 -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:
[ESRCH] No process was located using the which and who parameter values
[EINVAL] 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:
[EPERM] The process does not have ownership rights with respect to the
target process's real user ID.
[EACCES] The process is trying to raise its priority and does not have the
Functions: exec(2), nice(3)