pthread_getcpuclockid(3)

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

6       pthread_getcpuclockid - retrieve ID of a thread's CPU time clock
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SYNOPSIS

9       #include <pthread.h>
10       #include <time.h>
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12       int pthread_getcpuclockid(pthread_t thread, clockid_t *clockid);
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14       Compile and link with -pthread.
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DESCRIPTION

17       The  pthread_getcpuclockid()  function  obtains  the ID of the CPU-time
18       clock of the thread whose ID is given in thread, and returns it in  the
19       location pointed to by clockid.
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RETURN VALUE

22       On success, this function returns 0; on error, it returns a nonzero er‐
23       ror number.
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ERRORS

26       ENOENT Per-thread CPU time clocks are not supported by the system.
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28       ESRCH  No thread with the ID thread could be found.
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VERSIONS

31       This function is available in glibc since version 2.2.
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ATTRIBUTES

34       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
35       tributes(7).
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37       ┌────────────────────────────────────────────┬───────────────┬─────────┐
38       │Interface                                   │ Attribute     │ Value   │
39       ├────────────────────────────────────────────┼───────────────┼─────────┤
40       │pthread_getcpuclockid()                     │ Thread safety │ MT-Safe │
41       └────────────────────────────────────────────┴───────────────┴─────────┘
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CONFORMING TO

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

47       When  thread  refers  to  the  calling thread, this function returns an
48       identifier that refers to the  same  clock  manipulated  by  clock_get‐
49       time(2)    and    clock_settime(2)    when    given    the   clock   ID
50       CLOCK_THREAD_CPUTIME_ID.
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EXAMPLES

53       The program below creates a thread and then  uses  clock_gettime(2)  to
54       retrieve  the  total process CPU time, and the per-thread CPU time con‐
55       sumed by the two threads.  The following shell session shows an example
56       run:
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58           $ ./a.out
59           Main thread sleeping
60           Subthread starting infinite loop
61           Main thread consuming some CPU time...
62           Process total CPU time:    1.368
63           Main thread CPU time:      0.376
64           Subthread CPU time:        0.992
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66   Program source
67
68       /* Link with "-lrt" */
69
70       #include <time.h>
71       #include <stdio.h>
72       #include <stdint.h>
73       #include <stdlib.h>
74       #include <unistd.h>
75       #include <pthread.h>
76       #include <string.h>
77       #include <errno.h>
78
79       #define handle_error(msg) \
80               do { perror(msg); exit(EXIT_FAILURE); } while (0)
81
82       #define handle_error_en(en, msg) \
83               do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)
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85       static void *
86       thread_start(void *arg)
87       {
88           printf("Subthread starting infinite loop\n");
89           for (;;)
90               continue;
91       }
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93       static void
94       pclock(char *msg, clockid_t cid)
95       {
96           struct timespec ts;
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98           printf("%s", msg);
99           if (clock_gettime(cid, &ts) == -1)
100               handle_error("clock_gettime");
101           printf("%4jd.%03ld\n", (intmax_t) ts.tv_sec, ts.tv_nsec / 1000000);
102       }
103
104       int
105       main(int argc, char *argv[])
106       {
107           pthread_t thread;
108           clockid_t cid;
109           int s;
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111           s = pthread_create(&thread, NULL, thread_start, NULL);
112           if (s != 0)
113               handle_error_en(s, "pthread_create");
114
115           printf("Main thread sleeping\n");
116           sleep(1);
117
118           printf("Main thread consuming some CPU time...\n");
119           for (int j = 0; j < 2000000; j++)
120               getppid();
121
122           pclock("Process total CPU time: ", CLOCK_PROCESS_CPUTIME_ID);
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124           s = pthread_getcpuclockid(pthread_self(), &cid);
125           if (s != 0)
126               handle_error_en(s, "pthread_getcpuclockid");
127           pclock("Main thread CPU time:   ", cid);
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129           /* The preceding 4 lines of code could have been replaced by:
130              pclock("Main thread CPU time:   ", CLOCK_THREAD_CPUTIME_ID); */
131
132           s = pthread_getcpuclockid(thread, &cid);
133           if (s != 0)
134               handle_error_en(s, "pthread_getcpuclockid");
135           pclock("Subthread CPU time: 1    ", cid);
136
137           exit(EXIT_SUCCESS);         /* Terminates both threads */
138       }
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COLOPHON

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146       description  of  the project, information about reporting bugs, and the
147       latest    version    of    this    page,    can     be     found     at
148       https://www.kernel.org/doc/man-pages/.
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152Linux                             2021-03-22          PTHREAD_GETCPUCLOCKID(3)