getrusage man page on ElementaryOS

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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 statis‐
	      tics  will include the resources used by grandchildren, and fur‐
	      ther 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 following 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 filesystem had to perform input.

       ru_oublock (since Linux 2.6.22)
	      The number of times the filesystem 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 porta‐
       bility.	(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 automat‐
       ically included in the  value  returned	by  RUSAGE_CHILDREN,  although
       POSIX.1-2001  explicitly prohibits this.	 This nonconformance is recti‐
       fied 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 3.54 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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