GETRUSAGE(2)

NAME
getrusage - get information about resource utilization

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

#define RUSAGE_SELF 0
#define RUSAGE_CHILDREN -1
int
getrusage(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 either 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 */
            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
Upon success, a value of zero is returned. Otherwise, -1 is returned and errno is set to indicate the error.

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)

HISTORY
The getrusage() function call appeared in 4.2BSD.

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