GETRUSAGE(2)

NAME
getrusage - get information about resource utilization

SYNOPSIS
#include <sys/resource.h>
int
getrusage(int who, struct rusage *rusage);

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

RUSAGE_SELF
    Resources used by the current process.

RUSAGE_CHILDREN
    Resources used by all the terminated children of the current process which were waited upon. If the child is never waited for, the resource information for the child process is discarded.

RUSAGE_THREAD
    Resources used by the current thread.

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 */
            long ru_maxrss;          /* max resident set size */
            long ru_ixrss;           /* integral shared text memory size */
            long ru_idrss;           /* integral unshared data size */
            long ru_isrss;           /* integral unshared stack size */
            long ru_minflt;          /* page reclaims */
            long ru_majflt;          /* page faults */
            long ru_nswap;           /* swaps */
            long ru_inblock;         /* block input operations */
            long ru_oublock;         /* block output operations */
            long ru_msgsnd;          /* messages sent */
            long ru_msgrcv;          /* messages received */
            long ru_nsignals;        /* signals received */
            long ru_nvcsw;           /* voluntary context switches */
            long 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 * ticks-of-execution.

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

RETURN VALUES

ERRORS
getrusage() will fail if:

[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
clock_gettime(2), gettimeofday(2), wait(2)

STANDARDS
The getrusage() function conforms to p1003.1-2008.

The RUSAGE_THREAD flag is an extension to that specification.

HISTORY
A predecessor to getrusage(), times(), first appeared in AT&T UNIX. The getrusage() system call first appeared in 4.1cBSD.

The RUSAGE_THREAD flag has been available since OpenBSD 4.8.

BUGS
There is no way to obtain information about a child process that has not yet terminated or has not been waited for by the parent.