getrusage(2)
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
_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 appropriately.
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
getrusage() Thread safety MT-Safe
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD. POSIX.1 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).
SEE ALSO
clock_gettime(2), getrlimit(2), times(2), wait(2), wait4(2), clock(3)
COLOPHON
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latest version of this page, can be found at
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