man3/clock_getcpuclockid.3

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  26 .TH CLOCK_GETCPUCLOCKID 3 2017-09-15 "Linux" "Linux Programmer's Manual"
  27 .SH NAME
  28 clock_getcpuclockid \- obtain ID of a process CPU-time clock
  29 .SH SYNOPSIS
  30 .B #include <time.h>
  31 .nf
  32 .PP
  33 .BI "int clock_getcpuclockid(pid_t " pid ", clockid_t *" clock_id );
  34 .fi
  35 .PP
  36 Link with \fI\-lrt\fP (only for glibc versions before 2.17).
  37 .PP
  38 .ad l
  39 .in -4n
  40 Feature Test Macro Requirements for glibc (see
  41 .BR feature_test_macros (7)):
  42 .in
  43 .PP
  44 .BR clock_getcpuclockid ():
  45 .RS 4
  46 _POSIX_C_SOURCE\ >=\ 200112L
  47 .RE
  48 .ad
  49 .SH DESCRIPTION
  50 The
  51 .BR clock_getcpuclockid ()
  52 function obtains the ID of the CPU-time clock of the process whose ID is
  53 .IR pid ,
  54 and returns it in the location pointed to by
  55 .IR clock_id .
  56 If
  57 .I pid
  58 is zero, then the clock ID of the CPU-time clock
  59 of the calling process is returned.
  60 .SH RETURN VALUE
  61 On success,
  62 .BR clock_getcpuclockid ()
  63 returns 0;
  64 on error, it returns one of the positive error numbers listed in ERRORS.
  65 .SH ERRORS
  66 .TP
  67 .B ENOSYS
  68 The kernel does not support obtaining the per-process
  69 CPU-time clock of another process, and
  70 .I pid
  71 does not specify the calling process.
  72 .TP
  73 .B EPERM
  74 The caller does not have permission to access
  75 the CPU-time clock of the process specified by
  76 .IR pid .
  77 (Specified in POSIX.1-2001;
  78 does not occur on Linux unless the kernel does not support
  79 obtaining the per-process CPU-time clock of another process.)
  80 .TP
  81 .B ESRCH
  82 There is no process with the ID
  83 .IR pid .
  84 .SH VERSIONS
  85 The
  86 .BR clock_getcpuclockid ()
  87 function is available in glibc since version 2.2.
  88 .SH ATTRIBUTES
  89 For an explanation of the terms used in this section, see
  90 .BR attributes (7).
  91 .TS
  92 allbox;
  93 lbw21 lb lb
  94 l l l.
  95 Interface       Attribute       Value
  96 T{
  97 .BR clock_getcpuclockid ()
  98 T}      Thread safety   MT-Safe
  99 .TE
 100 .SH CONFORMING TO
 101 POSIX.1-2001, POSIX.1-2008.
 102 .SH NOTES
 103 Calling
 104 .BR clock_gettime (2)
 105 with the clock ID obtained by a call to
 106 .BR clock_getcpuclockid ()
 107 with a
 108 .I pid
 109 of 0,
 110 is the same as using the clock ID
 111 .BR CLOCK_PROCESS_CPUTIME_ID .
 112 .SH EXAMPLE
 113 The example program below obtains the
 114 CPU-time clock ID of the process whose ID is given on the command line,
 115 and then uses
 116 .BR clock_gettime (2)
 117 to obtain the time on that clock.
 118 An example run is the following:
 119 .PP
 120 .in +4n
 121 .EX
 122 .RB "$" " ./a.out 1" "                 # Show CPU clock of init process"
 123 CPU-time clock for PID 1 is 2.213466748 seconds
 124 .EE
 125 .in
 126 .SS Program source
 127 \&
 128 .EX
 129 #define _XOPEN_SOURCE 600
 130 #include <stdio.h>
 131 #include <unistd.h>
 132 #include <stdlib.h>
 133 #include <time.h>
 134
 135 int
 136 main(int argc, char *argv[])
 137 {
 138     clockid_t clockid;
 139     struct timespec ts;
 140
 141     if (argc != 2) {
 142         fprintf(stderr, "%s <process\-ID>\\n", argv[0]);
 143         exit(EXIT_FAILURE);
 144     }
 145
 146     if (clock_getcpuclockid(atoi(argv[1]), &clockid) != 0) {
 147         perror("clock_getcpuclockid");
 148         exit(EXIT_FAILURE);
 149     }
 150
 151     if (clock_gettime(clockid, &ts) == \-1) {
 152         perror("clock_gettime");
 153         exit(EXIT_FAILURE);
 154     }
 155
 156     printf("CPU-time clock for PID %s is %ld.%09ld seconds\\n",
 157             argv[1], (long) ts.tv_sec, (long) ts.tv_nsec);
 158     exit(EXIT_SUCCESS);
 159 }
 160 .EE
 161 .SH SEE ALSO
 162 .BR clock_getres (2),
 163 .BR timer_create (2),
 164 .BR pthread_getcpuclockid (3),
 165 .BR time (7)