man2/getrusage.2

   1 .\" Copyright (c) 1992 Drew Eckhardt, March 28, 1992
   2 .\" and Copyright (c) 2002 Michael Kerrisk
   3 .\"
   4 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   5 .\"
   6 .\" 2004-11-16 -- mtk: the getrlimit.2 page, which formerly included
   7 .\" coverage of getrusage(2), has been split, so that the latter is
   8 .\" now covered in its own getrusage.2.  For older details of change
   9 .\" history, etc., see getrlimit.2
  10 .\"
  11 .\" Modified 2004-11-16, mtk, Noted that the nonconformance
  12 .\"     when SIGCHLD is being ignored is fixed in 2.6.9.
  13 .\" 2008-02-22, Sripathi Kodi <sripathik@in.ibm.com>: Document RUSAGE_THREAD
  14 .\" 2008-05-25, mtk, clarify RUSAGE_CHILDREN + other clean-ups.
  15 .\" 2010-05-24, Mark Hills <mark@pogo.org.uk>: Description of fields,
  16 .\"     document ru_maxrss
  17 .\" 2010-05-24, mtk, enhanced description of various fields
  18 .\"
  19 .TH GETRUSAGE 2 2021-03-22 "Linux" "Linux Programmer's Manual"
  20 .SH NAME
  21 getrusage \- get resource usage
  22 .SH LIBRARY
  23 Standard C library
  24 .RI ( libc ", " \-lc )
  25 .SH SYNOPSIS
  26 .nf
  27 .B #include <sys/resource.h>
  28 .PP
  29 .BI "int getrusage(int " who ", struct rusage *" usage );
  30 .fi
  31 .SH DESCRIPTION
  32 .BR getrusage ()
  33 returns resource usage measures for
  34 .IR who ,
  35 which can be one of the following:
  36 .TP
  37 .B RUSAGE_SELF
  38 Return resource usage statistics for the calling process,
  39 which is the sum of resources used by all threads in the process.
  40 .TP
  41 .B RUSAGE_CHILDREN
  42 Return resource usage statistics for all children of the
  43 calling process that have terminated and been waited for.
  44 These statistics will include the resources used by grandchildren,
  45 and further removed descendants,
  46 if all of the intervening descendants waited on their terminated children.
  47 .TP
  48 .BR RUSAGE_THREAD " (since Linux 2.6.26)"
  49 Return resource usage statistics for the calling thread.
  50 The
  51 .B _GNU_SOURCE
  52 feature test macro must be defined (before including
  53 .I any
  54 header file)
  55 in order to obtain the definition of this constant from
  56 .IR <sys/resource.h> .
  57 .PP
  58 The resource usages are returned in the structure pointed to by
  59 .IR usage ,
  60 which has the following form:
  61 .PP
  62 .in +4n
  63 .EX
  64 struct rusage {
  65     struct timeval ru_utime; /* user CPU time used */
  66     struct timeval ru_stime; /* system CPU time used */
  67     long   ru_maxrss;        /* maximum resident set size */
  68     long   ru_ixrss;         /* integral shared memory size */
  69     long   ru_idrss;         /* integral unshared data size */
  70     long   ru_isrss;         /* integral unshared stack size */
  71     long   ru_minflt;        /* page reclaims (soft page faults) */
  72     long   ru_majflt;        /* page faults (hard page faults) */
  73     long   ru_nswap;         /* swaps */
  74     long   ru_inblock;       /* block input operations */
  75     long   ru_oublock;       /* block output operations */
  76     long   ru_msgsnd;        /* IPC messages sent */
  77     long   ru_msgrcv;        /* IPC messages received */
  78     long   ru_nsignals;      /* signals received */
  79     long   ru_nvcsw;         /* voluntary context switches */
  80     long   ru_nivcsw;        /* involuntary context switches */
  81 };
  82 .EE
  83 .in
  84 .PP
  85 Not all fields are completed;
  86 unmaintained fields are set to zero by the kernel.
  87 (The unmaintained fields are provided for compatibility with other systems,
  88 and because they may one day be supported on Linux.)
  89 The fields are interpreted as follows:
  90 .TP
  91 .I ru_utime
  92 This is the total amount of time spent executing in user mode,
  93 expressed in a
  94 .I timeval
  95 structure (seconds plus microseconds).
  96 .TP
  97 .I ru_stime
  98 This is the total amount of time spent executing in kernel mode,
  99 expressed in a
 100 .I timeval
 101 structure (seconds plus microseconds).
 102 .TP
 103 .IR ru_maxrss " (since Linux 2.6.32)"
 104 This is the maximum resident set size used (in kilobytes).
 105 For
 106 .BR RUSAGE_CHILDREN ,
 107 this is the resident set size of the largest child, not the maximum
 108 resident set size of the process tree.
 109 .TP
 110 .IR ru_ixrss " (unmaintained)"
 111 This field is currently unused on Linux.
 112 .\" On some systems,
 113 .\" this is the integral of the text segment memory consumption,
 114 .\" expressed in kilobyte-seconds.
 115 .TP
 116 .IR ru_idrss " (unmaintained)"
 117 This field is currently unused on Linux.
 118 .\" On some systems, this is the integral of the data segment memory consumption,
 119 .\" expressed in kilobyte-seconds.
 120 .TP
 121 .IR ru_isrss " (unmaintained)"
 122 This field is currently unused on Linux.
 123 .\" On some systems, this is the integral of the stack memory consumption,
 124 .\" expressed in kilobyte-seconds.
 125 .TP
 126 .I ru_minflt
 127 The number of page faults serviced without any I/O activity; here
 128 I/O activity is avoided by \*(lqreclaiming\*(rq a page frame from
 129 the list of pages awaiting reallocation.
 130 .TP
 131 .I ru_majflt
 132 The number of page faults serviced that required I/O activity.
 133 .TP
 134 .IR ru_nswap  " (unmaintained)"
 135 This field is currently unused on Linux.
 136 .\" On some systems, this is the number of swaps out of physical memory.
 137 .TP
 138 .IR ru_inblock " (since Linux 2.6.22)"
 139 The number of times the filesystem had to perform input.
 140 .TP
 141 .IR ru_oublock " (since Linux 2.6.22)"
 142 The number of times the filesystem had to perform output.
 143 .TP
 144 .IR ru_msgsnd " (unmaintained)"
 145 This field is currently unused on Linux.
 146 .\" On FreeBSD 6.2, this appears to measure messages sent over sockets
 147 .\" On some systems,
 148 .\" this field records the number of messages sent over sockets.
 149 .TP
 150 .IR ru_msgrcv " (unmaintained)"
 151 This field is currently unused on Linux.
 152 .\" On FreeBSD 6.2, this appears to measure messages received over sockets
 153 .\" On some systems,
 154 .\" this field records the number of messages received over sockets.
 155 .TP
 156 .IR ru_nsignals " (unmaintained)"
 157 This field is currently unused on Linux.
 158 .\" On some systems, this field records the number of signals received.
 159 .TP
 160 .IR ru_nvcsw " (since Linux 2.6)"
 161 The number of times a context switch resulted due to a process
 162 voluntarily giving up the processor before its time slice was
 163 completed (usually to await availability of a resource).
 164 .TP
 165 .IR ru_nivcsw " (since Linux 2.6)"
 166 The number of times a context switch resulted due to a higher
 167 priority process becoming runnable or because the current process
 168 exceeded its time slice.
 169 .SH RETURN VALUE
 170 On success, zero is returned.
 171 On error, \-1 is returned, and
 172 .I errno
 173 is set to indicate the error.
 174 .SH ERRORS
 175 .TP
 176 .B EFAULT
 177 .I usage
 178 points outside the accessible address space.
 179 .TP
 180 .B EINVAL
 181 .I who
 182 is invalid.
 183 .SH ATTRIBUTES
 184 For an explanation of the terms used in this section, see
 185 .BR attributes (7).
 186 .ad l
 187 .nh
 188 .TS
 189 allbox;
 190 lbx lb lb
 191 l l l.
 192 Interface       Attribute       Value
 193 T{
 194 .BR getrusage ()
 195 T}      Thread safety   MT-Safe
 196 .TE
 197 .hy
 198 .ad
 199 .sp 1
 200 .SH CONFORMING TO
 201 POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
 202 POSIX.1 specifies
 203 .BR getrusage (),
 204 but specifies only the fields
 205 .I ru_utime
 206 and
 207 .IR ru_stime .
 208 .PP
 209 .B RUSAGE_THREAD
 210 is Linux-specific.
 211 .SH NOTES
 212 Resource usage metrics are preserved across an
 213 .BR execve (2).
 214 .PP
 215 In Linux kernel versions before 2.6.9, if the disposition of
 216 .B SIGCHLD
 217 is set to
 218 .B SIG_IGN
 219 then the resource usages of child processes
 220 are automatically included in the value returned by
 221 .BR RUSAGE_CHILDREN ,
 222 although POSIX.1-2001 explicitly prohibits this.
 223 This nonconformance is rectified in Linux 2.6.9 and later.
 224 .\" See the description of getrusage() in XSH.
 225 .\" A similar statement was also in SUSv2.
 226 .PP
 227 The structure definition shown at the start of this page
 228 was taken from 4.3BSD Reno.
 229 .PP
 230 Ancient systems provided a
 231 .BR vtimes ()
 232 function with a similar purpose to
 233 .BR getrusage ().
 234 For backward compatibility, glibc (up until version 2.32) also provides
 235 .BR vtimes ().
 236 All new applications should be written using
 237 .BR getrusage ().
 238 (Since version 2.33, glibc no longer provides an
 239 .BR vtimes ()
 240 implementation.)
 241 .PP
 242 See also the description of
 243 .IR /proc/ pid /stat
 244 in
 245 .BR proc (5).
 246 .SH SEE ALSO
 247 .BR clock_gettime (2),
 248 .BR getrlimit (2),
 249 .BR times (2),
 250 .BR wait (2),
 251 .BR wait4 (2),
 252 .BR clock (3)