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GETRUSAGE(2)			    Linux Programmer's Manual			     GETRUSAGE(2)

NAME
       getrusage - get resource usage

SYNOPSIS
       #include <sys/time.h>
       #include <sys/resource.h>

       int getrusage(int who, struct rusage *usage);

DESCRIPTION
       getrusage() returns resource usage measures for who, which can be one of the following:

       RUSAGE_SELF
	      Return  resource	usage  statistics  for	the  calling process, which is the sum of
	      resources used by all threads in the process.

       RUSAGE_CHILDREN
	      Return resource usage statistics for all children of the calling process that  have
	      terminated  and  been waited for.  These statistics will include the resources used
	      by grandchildren, and further  removed  descendants,  if	all  of  the  intervening
	      descendants waited on their terminated children.

       RUSAGE_THREAD (since Linux 2.6.26)
	      Return resource usage statistics for the calling thread.

       The  resource usages are returned in the structure pointed to by usage, which has the fol-
       lowing form:

	   struct rusage {
	       struct timeval ru_utime; /* user CPU time used */
	       struct timeval ru_stime; /* system CPU time used */
	       long   ru_maxrss;	/* maximum resident set size */
	       long   ru_ixrss; 	/* integral shared memory size */
	       long   ru_idrss; 	/* integral unshared data size */
	       long   ru_isrss; 	/* integral unshared stack size */
	       long   ru_minflt;	/* page reclaims (soft page faults) */
	       long   ru_majflt;	/* page faults (hard page faults) */
	       long   ru_nswap; 	/* swaps */
	       long   ru_inblock;	/* block input operations */
	       long   ru_oublock;	/* block output operations */
	       long   ru_msgsnd;	/* IPC messages sent */
	       long   ru_msgrcv;	/* IPC messages received */
	       long   ru_nsignals;	/* signals received */
	       long   ru_nvcsw; 	/* voluntary context switches */
	       long   ru_nivcsw;	/* involuntary context switches */
	   };

       Not all fields are completed; unmaintained fields are set to zero  by  the  kernel.   (The
       unmaintained  fields  are  provided for compatibility with other systems, and because they
       may one day be supported on Linux.)  The fields are interpreted as follows:

       ru_utime
	      This is the total amount of time spent executing	in  user  mode,  expressed  in	a
	      timeval structure (seconds plus microseconds).

       ru_stime
	      This  is	the  total  amount of time spent executing in kernel mode, expressed in a
	      timeval structure (seconds plus microseconds).

       ru_maxrss (since Linux 2.6.32)
	      This is the maximum resident set size used (in  kilobytes).   For  RUSAGE_CHILDREN,
	      this  is	the  resident set size of the largest child, not the maximum resident set
	      size of the process tree.

       ru_ixrss (unmaintained)
	      This field is currently unused on Linux.

       ru_idrss (unmaintained)
	      This field is currently unused on Linux.

       ru_isrss (unmaintained)
	      This field is currently unused on Linux.

       ru_minflt
	      The number of page faults serviced without any I/O activity; here I/O  activity  is
	      avoided by "reclaiming" a page frame from the list of pages awaiting reallocation.

       ru_majflt
	      The number of page faults serviced that required I/O activity.

       ru_nswap (unmaintained)
	      This field is currently unused on Linux.

       ru_inblock (since Linux 2.6.22)
	      The number of times the file system had to perform input.

       ru_oublock (since Linux 2.6.22)
	      The number of times the file system had to perform output.

       ru_msgsnd (unmaintained)
	      This field is currently unused on Linux.

       ru_msgrcv (unmaintained)
	      This field is currently unused on Linux.

       ru_nsignals (unmaintained)
	      This field is currently unused on Linux.

       ru_nvcsw (since Linux 2.6)
	      The  number  of times a context switch resulted due to a process voluntarily giving
	      up the processor before its time slice was completed (usually to await availability
	      of a resource).

       ru_nivcsw (since Linux 2.6)
	      The  number  of  times  a  context switch resulted due to a higher priority process
	      becoming runnable or because the current process exceeded its time slice.

RETURN VALUE
       On success, zero is returned.  On error, -1 is returned, and errno is set appropriately.

ERRORS
       EFAULT usage points outside the accessible address space.

       EINVAL who is invalid.

CONFORMING TO
       SVr4, 4.3BSD.  POSIX.1-2001 specifies getrusage(), but specifies only the fields  ru_utime
       and ru_stime.

       RUSAGE_THREAD is Linux-specific.

NOTES
       Resource usage metrics are preserved across an execve(2).

       Including  <sys/time.h>	is  not required these days, but increases portability.  (Indeed,
       struct timeval is defined in <sys/time.h>.)

       In Linux kernel versions before 2.6.9, if the disposition of SIGCHLD  is  set  to  SIG_IGN
       then  the  resource  usages  of	child  processes  are automatically included in the value
       returned by RUSAGE_CHILDREN, although POSIX.1-2001 explicitly prohibits this.   This  non-
       conformance is rectified in Linux 2.6.9 and later.

       The structure definition shown at the start of this page was taken from 4.3BSD Reno.

       Ancient	systems  provided a vtimes() function with a similar purpose to getrusage().  For
       backward compatibility, glibc also provides vtimes().   All  new  applications  should  be
       written using getrusage().

       See also the description of /proc/PID/stat in proc(5).

SEE ALSO
       clock_gettime(2), getrlimit(2), times(2), wait(2), wait4(2), clock(3)

COLOPHON
       This  page  is  part of release 3.53 of the Linux man-pages project.  A description of the
       project,    and	  information	 about	  reporting    bugs,	can    be    found     at
       http://www.kernel.org/doc/man-pages/.

Linux					    2010-09-26				     GETRUSAGE(2)
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