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
38              obtaining 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
48       attributes(7).
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50       ┌──────────────────────┬───────────────┬─────────┐
51       │Interface             │ Attribute     │ Value   │
52       ├──────────────────────┼───────────────┼─────────┤
53       │clock_getcpuclockid() │ Thread safety │ MT-Safe │
54       └──────────────────────┴───────────────┴─────────┘

CONFORMING TO

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

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

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

109       This page is part of release 5.07 of the Linux  man-pages  project.   A
110       description  of  the project, information about reporting bugs, and the
111       latest    version    of    this    page,    can     be     found     at
112       https://www.kernel.org/doc/man-pages/.
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116Linux                             2020-06-09            CLOCK_GETCPUCLOCKID(3)