GETRUSAGE(2)

NAME
getrusage - get information about resource utilization

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

#define	RUSAGE_SELF	0	/* calling process */
#define	RUSAGE_CHILDREN	-1	/* terminated child processes */

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

DESCRIPTION
Getrusage returns information describing the resources utilized by the current process, or all its terminated child processes. The who parameter is one of RUSAGE_SELF or RUSAGE_CHILDREN. The buffer to which rusage points will be filled in with the following structure:

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

The fields are interpreted as follows:

ru_utime
    the total amount of time spent executing in user mode.

ru_stime
    the total amount of time spent in the system executing on behalf of the process(es).

ru_maxrss
    the maximum resident set size utilized (in kilobytes).

ru_ixrss
    an “integral” value indicating the amount of memory used by the text segment that was also shared among other processes. This value is expressed in units of kilobytes * seconds-of-execution and is calculated by summing the number of shared memory pages in use each time the internal system clock ticks and then averaging over 1 second intervals.

ru_idrss
    an integral value of the amount of unshared memory residing in the data segment of a process (expressed in units of kilobytes * seconds-of-execution).

ru_isrss
    an integral value of the amount of unshared memory residing in the stack segment of a process (expressed in units of kilobytes * seconds-of-execution).

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
    the number of times a process was “swapped” out of main memory.

ru_inblock
    the number of times the file system had to perform input.

ru_outblock
    the number of times the file system had to perform output.

ru_msgsnd
    the number of IPC messages sent.

ru_msgrcv
    the number of IPC messages received.

ru_nsignals
    the number of signals delivered.

ru_nvcsw
    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
    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.

NOTES
The numbers ru_inblock and ru_outblock account only for real I/O; data supplied by the caching mechanism is charged only to the first process to read or write the data.

ERRORS
The possible errors for getrusage are:

[EINVAL]
    The who parameter is not a valid value.

[EFAULT]
    The address specified by the rusage parameter is not in a valid part of the process address space.

SEE ALSO
gettimeofday(2), wait(2)

BUGS
There is no way to obtain information about a child process that has not yet terminated.