pthread_getcpuclockid(3)

1pthread_getcpuclockid(3)   Library Functions 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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LIBRARY

9       POSIX threads library (libpthread, -lpthread)
10

SYNOPSIS

12       #include <pthread.h>
13       #include <time.h>
14
15       int pthread_getcpuclockid(pthread_t thread, clockid_t *clockid);
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DESCRIPTION

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

23       On success, this function returns 0; on error, it returns a nonzero er‐
24       ror number.
25

ERRORS

27       ENOENT Per-thread CPU time clocks are not supported by the system.
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29       ESRCH  No thread with the ID thread could be found.
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ATTRIBUTES

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

42       POSIX.1-2008.
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HISTORY

45       glibc 2.2.  POSIX.1-2001.
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NOTES

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

54       The program below creates a thread and then  uses  clock_gettime(2)  to
55       retrieve  the  total process CPU time, and the per-thread CPU time con‐
56       sumed by the two threads.  The following shell session shows an example
57       run:
58
59           $ ./a.out
60           Main thread sleeping
61           Subthread starting infinite loop
62           Main thread consuming some CPU time...
63           Process total CPU time:    1.368
64           Main thread CPU time:      0.376
65           Subthread CPU time:        0.992
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67   Program source
68
69       /* Link with "-lrt" */
70
71       #include <errno.h>
72       #include <pthread.h>
73       #include <stdint.h>
74       #include <stdio.h>
75       #include <stdlib.h>
76       #include <string.h>
77       #include <time.h>
78       #include <unistd.h>
79
80       #define handle_error(msg) \
81               do { perror(msg); exit(EXIT_FAILURE); } while (0)
82
83       #define handle_error_en(en, msg) \
84               do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)
85
86       static void *
87       thread_start(void *arg)
88       {
89           printf("Subthread starting infinite loop\n");
90           for (;;)
91               continue;
92       }
93
94       static void
95       pclock(char *msg, clockid_t cid)
96       {
97           struct timespec ts;
98
99           printf("%s", msg);
100           if (clock_gettime(cid, &ts) == -1)
101               handle_error("clock_gettime");
102           printf("%4jd.%03ld\n", (intmax_t) ts.tv_sec, ts.tv_nsec / 1000000);
103       }
104
105       int
106       main(void)
107       {
108           pthread_t thread;
109           clockid_t cid;
110           int s;
111
112           s = pthread_create(&thread, NULL, thread_start, NULL);
113           if (s != 0)
114               handle_error_en(s, "pthread_create");
115
116           printf("Main thread sleeping\n");
117           sleep(1);
118
119           printf("Main thread consuming some CPU time...\n");
120           for (unsigned int j = 0; j < 2000000; j++)
121               getppid();
122
123           pclock("Process total CPU time: ", CLOCK_PROCESS_CPUTIME_ID);
124
125           s = pthread_getcpuclockid(pthread_self(), &cid);
126           if (s != 0)
127               handle_error_en(s, "pthread_getcpuclockid");
128           pclock("Main thread CPU time:   ", cid);
129
130           /* The preceding 4 lines of code could have been replaced by:
131              pclock("Main thread CPU time:   ", CLOCK_THREAD_CPUTIME_ID); */
132
133           s = pthread_getcpuclockid(thread, &cid);
134           if (s != 0)
135               handle_error_en(s, "pthread_getcpuclockid");
136           pclock("Subthread CPU time: 1    ", cid);
137
138           exit(EXIT_SUCCESS);         /* Terminates both threads */
139       }
140