getrusage(2)

NAME
getrusage - get resource usage

LIBRARY
Standard C library (libc, -lc)

SYNOPSIS
#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 _GNU_SOURCE feature test macro must be defined (before including any header file) in order to obtain the definition of this constant from <sys/resource.h>.

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 to indicate the error.

ERRORS

EFAULT
    usage points outside the accessible address space.

EINVAL
    who is invalid.

ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
Interface | Attribute | Value
 | Thread safety | MT-Safe

STANDARDS
POSIX.1-2008.

POSIX.1 specifies getrusage(), but specifies only the fields ru_utime and ru_stime.

RUSAGE_THREAD is Linux-specific.

HISTORY
POSIX.1-2001, SVr4, 4.3BSD.

Before Linux 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 nonconformance 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 (up until Linux 2.32) also provides vtimes(). All new applications should be written using getrusage(). (Since Linux 2.33, glibc no longer provides an vtimes() implementation.)

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

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)