clock_getcpuclockid(3)

1CLOCK_GETCPUCLOCKID(3)     Linux Programmer's Manual    CLOCK_GETCPUCLOCKID(3)
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NAME

6       clock_getcpuclockid - obtain ID of a process CPU-time clock
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SYNOPSIS

9       #include <time.h>
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11       int clock_getcpuclockid(pid_t pid, clockid_t *clockid);
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13       Link with -lrt (only for glibc versions before 2.17).
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15   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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17       clock_getcpuclockid():
18           _POSIX_C_SOURCE >= 200112L
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DESCRIPTION

21       The clock_getcpuclockid() function obtains the ID of the CPU-time clock
22       of the process whose ID is pid, and returns it in the location pointed
23       to by clockid.  If pid is zero, then the clock ID of the CPU-time clock
24       of the calling process is returned.
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RETURN VALUE

27       On success, clock_getcpuclockid() returns 0; on error, it returns one
28       of the positive error numbers listed in ERRORS.
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ERRORS

31       ENOSYS The kernel does not support obtaining the per-process CPU-time
32              clock of another process, and pid does not specify the calling
33              process.
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35       EPERM  The caller does not have permission to access the CPU-time clock
36              of the process specified by pid.  (Specified in POSIX.1-2001;
37              does not occur on Linux unless the kernel does not support ob‐
38              taining the per-process CPU-time clock of another process.)
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40       ESRCH  There is no process with the ID pid.
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VERSIONS

43       The clock_getcpuclockid() function is available in glibc since version
44       2.2.
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ATTRIBUTES

47       For an explanation of the terms used in this section, see at‐
48       tributes(7).
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50       ┌────────────────────────────────────────────┬───────────────┬─────────┐
51       │Interface                                   │ Attribute     │ Value   │
52       ├────────────────────────────────────────────┼───────────────┼─────────┤
53       │clock_getcpuclockid()                       │ Thread safety │ MT-Safe │
54       └────────────────────────────────────────────┴───────────────┴─────────┘
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CONFORMING TO

57       POSIX.1-2001, POSIX.1-2008.
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NOTES

60       Calling clock_gettime(2) with the  clock  ID  obtained  by  a  call  to
61       clock_getcpuclockid()  with  a pid of 0, is the same as using the clock
62       ID CLOCK_PROCESS_CPUTIME_ID.
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EXAMPLES

65       The example program below obtains the CPU-time clock ID of the  process
66       whose  ID  is given on the command line, and then uses clock_gettime(2)
67       to obtain the time on that clock.  An example run is the following:
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69           $ ./a.out 1                 # Show CPU clock of init process
70           CPU-time clock for PID 1 is 2.213466748 seconds
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72   Program source
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74       #define _XOPEN_SOURCE 600
75       #include <stdint.h>
76       #include <stdio.h>
77       #include <unistd.h>
78       #include <stdlib.h>
79       #include <time.h>
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81       int
82       main(int argc, char *argv[])
83       {
84           clockid_t clockid;
85           struct timespec ts;
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87           if (argc != 2) {
88               fprintf(stderr, "%s <process-ID>\n", argv[0]);
89               exit(EXIT_FAILURE);
90           }
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92           if (clock_getcpuclockid(atoi(argv[1]), &clockid) != 0) {
93               perror("clock_getcpuclockid");
94               exit(EXIT_FAILURE);
95           }
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97           if (clock_gettime(clockid, &ts) == -1) {
98               perror("clock_gettime");
99               exit(EXIT_FAILURE);
100           }
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102           printf("CPU-time clock for PID %s is %jd.%09ld seconds\n",
103                   argv[1], (intmax_t) ts.tv_sec, ts.tv_nsec);
104           exit(EXIT_SUCCESS);
105       }
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COLOPHON

111       This page is part of release 5.13 of the Linux  man-pages  project.   A
112       description  of  the project, information about reporting bugs, and the
113       latest    version    of    this    page,    can     be     found     at
114       https://www.kernel.org/doc/man-pages/.
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118Linux                             2021-03-22            CLOCK_GETCPUCLOCKID(3)