clock_getcpuclockid(3)

1clock_getcpuclockid(3)     Library Functions Manual     clock_getcpuclockid(3)
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NAME

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

9       Standard C library (libc, -lc), since glibc 2.17
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11       Before glibc 2.17, Real-time library (librt, -lrt)
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SYNOPSIS

14       #include <time.h>
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16       int clock_getcpuclockid(pid_t pid, clockid_t *clockid);
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18   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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20       clock_getcpuclockid():
21           _POSIX_C_SOURCE >= 200112L
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DESCRIPTION

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

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

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

46       For an explanation of the terms used in this section, see at‐
47       tributes(7).
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49       ┌────────────────────────────────────────────┬───────────────┬─────────┐
50       │Interface                                   │ Attribute     │ Value   │
51       ├────────────────────────────────────────────┼───────────────┼─────────┤
52       │clock_getcpuclockid()                       │ Thread safety │ MT-Safe │
53       └────────────────────────────────────────────┴───────────────┴─────────┘
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STANDARDS

56       POSIX.1-2008.
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HISTORY

59       glibc 2.2.  POSIX.1-2001.
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NOTES

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

67       The example program below obtains the CPU-time clock ID of the process
68       whose ID is given on the command line, and then uses clock_gettime(2)
69       to obtain the time on that clock.  An example run is the following:
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71           $ ./a.out 1                 # Show CPU clock of init process
72           CPU-time clock for PID 1 is 2.213466748 seconds
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74   Program source
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76       #define _XOPEN_SOURCE 600
77       #include <stdint.h>
78       #include <stdio.h>
79       #include <stdlib.h>
80       #include <time.h>
81       #include <unistd.h>
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83       int
84       main(int argc, char *argv[])
85       {
86           clockid_t clockid;
87           struct timespec ts;
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89           if (argc != 2) {
90               fprintf(stderr, "%s <process-ID>\n", argv[0]);
91               exit(EXIT_FAILURE);
92           }
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94           if (clock_getcpuclockid(atoi(argv[1]), &clockid) != 0) {
95               perror("clock_getcpuclockid");
96               exit(EXIT_FAILURE);
97           }
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99           if (clock_gettime(clockid, &ts) == -1) {
100               perror("clock_gettime");
101               exit(EXIT_FAILURE);
102           }
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104           printf("CPU-time clock for PID %s is %jd.%09ld seconds\n",
105                  argv[1], (intmax_t) ts.tv_sec, ts.tv_nsec);
106           exit(EXIT_SUCCESS);
107       }
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