getrusage (2)

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
NOTES
SEE ALSO
COLOPHON

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 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 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 portability. (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 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 also provides vtimes(). All new applications should be written using getrusage().

See also the description of /proc/PID/stat in proc(5).

COLOPHON

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