getrusage

       For a detailed description about the values returned by
       getrusage() please consult your usual C programming
       documentation about getrusage() and also the header file
       sys/resource.h.  The $ru_who argument is either
       RUSAGE_SELF (the current process) or RUSAGE_CHILDREN (all
       the child processes of the current process).  On some
       (very few) systems (those supporting both getrusage() and
       the POSIX threads) there is also RUSAGE_THREAD. The
       BSD::Resource supports the _THREAD flag if it is present
       but understands nothing about the POSIX threads
       themselves.

       Note 1: officially HP-UX 9 does not support getrusage() at
       all but for the time being, it does seem to.

       Note 2: Solaris claims in sys/rusage.h that the ixrss and
       the isrss fields are always zero.

       getrlimit

       Processes have soft and hard resource limits.  At soft
       limit they receive a signal (XCPU or XFSZ, normally) they
       can trap and handle and at hard limit they will be
       ruthlessly killed by the KILL signal.  The $resource
       argument can be one of

               RLIMIT_CPU RLIMIT_FSIZE
               RLIMIT_DATA RLIMIT_STACK RLIMIT_CORE RLIMIT_RSS
               RLIMIT_NOFILE RLIMIT_OPEN_MAX
               RLIMIT_AS RLIMIT_VMEM

       The last two pairs (NO_FILE, OPEN_MAX) and (AS, VMEM) mean
       the same, the former being the BSD names and the latter
       SVR4 names.  Two meta-resource-symbols might exist

               RLIM_NLIMITS
               RLIM_INFINITY

       NLIMITS being the number of possible (but not necessarily
       fully supported) resource limits, INFINITY being useful in
       setrlimit().

       NOTE: the level of 'support' for a resource varies. Not
       all the systems

               a) even recognise all those limits
               b) really track the consumption of a resource
               c) care (send those signals) if a resource limit get exceeded

       Again, please consult your usual C programming
       documentation.

       One notable exception: officially HP-UX 9 does not support
       getrlimit() at all but for the time being, it does seem
       to.

       getpriority

       The priorities returned by getpriority() are
       [PRIO_MIN,PRIO_MAX].  The $which argument can be any of
       PRIO_PROCESS (a process) PRIO_USER (a user), or PRIO_PGRP
       (a process group). The $pr_who argument tells which
       process/user/process group, 0 signifying the current one.

       setrlimit

       A normal user process can only lower its resource limits.
       Soft or hard limit RLIM_INFINITY means as much as
       possible, the real limits are normally buried inside the
       kernel.

       setpriority

       The priorities handled by setpriority() are
       [PRIO_MIN,PRIO_MAX].  A normal user process can only lower
       its priority (make it more positive).