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| .TH PTHREAD_GETCPUCLOCKID 3 2019-03-06 "Linux" "Linux Programmer's Manual" |
| .SH NAME |
| pthread_getcpuclockid \- retrieve ID of a thread's CPU time clock |
| .SH SYNOPSIS |
| .nf |
| .B #include <pthread.h> |
| .B #include <time.h> |
| .PP |
| .BI "int pthread_getcpuclockid(pthread_t " thread ", clockid_t *" clock_id ); |
| .PP |
| Compile and link with \fI\-pthread\fP. |
| .fi |
| .SH DESCRIPTION |
| The |
| .BR pthread_getcpuclockid () |
| function returns the clock ID for the CPU time clock of the thread |
| .IR thread . |
| .\" The clockid is constructed as follows: |
| .\" *clockid = CLOCK_THREAD_CPUTIME_ID | (pd->tid << CLOCK_IDFIELD_SIZE) |
| .\" where CLOCK_IDFIELD_SIZE is 3. |
| .SH RETURN VALUE |
| On success, this function returns 0; |
| on error, it returns a nonzero error number. |
| .SH ERRORS |
| .TP |
| .B ENOENT |
| .\" CLOCK_THREAD_CPUTIME_ID not defined |
| Per-thread CPU time clocks are not supported by the system. |
| .\" |
| .\" Looking at nptl/pthread_getcpuclockid.c an ERANGE error would |
| .\" be possible if kernel thread IDs took more than 29 bits (which |
| .\" they currently cannot). |
| .TP |
| .B ESRCH |
| No thread with the ID |
| .I thread |
| could be found. |
| .SH VERSIONS |
| This function is available in glibc since version 2.2. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .TS |
| allbox; |
| lbw23 lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR pthread_getcpuclockid () |
| T} Thread safety MT-Safe |
| .TE |
| .SH CONFORMING TO |
| POSIX.1-2001, POSIX.1-2008. |
| .SH NOTES |
| When |
| .I thread |
| refers to the calling thread, |
| this function returns an identifier that refers to the same clock |
| manipulated by |
| .BR clock_gettime (2) |
| and |
| .BR clock_settime (2) |
| when given the clock ID |
| .BR CLOCK_THREAD_CPUTIME_ID . |
| .SH EXAMPLE |
| The program below creates a thread and then uses |
| .BR clock_gettime (2) |
| to retrieve the total process CPU time, |
| and the per-thread CPU time consumed by the two threads. |
| The following shell session shows an example run: |
| .PP |
| .in +4n |
| .EX |
| $ \fB./a.out\fP |
| Main thread sleeping |
| Subthread starting infinite loop |
| Main thread consuming some CPU time... |
| Process total CPU time: 1.368 |
| Main thread CPU time: 0.376 |
| Subthread CPU time: 0.992 |
| .EE |
| .in |
| .SS Program source |
| \& |
| .EX |
| /* Link with "\-lrt" */ |
| |
| #include <time.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <unistd.h> |
| #include <pthread.h> |
| #include <string.h> |
| #include <errno.h> |
| |
| #define handle_error(msg) \e |
| do { perror(msg); exit(EXIT_FAILURE); } while (0) |
| |
| #define handle_error_en(en, msg) \e |
| do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0) |
| |
| static void * |
| thread_start(void *arg) |
| { |
| printf("Subthread starting infinite loop\en"); |
| for (;;) |
| continue; |
| } |
| |
| static void |
| pclock(char *msg, clockid_t cid) |
| { |
| struct timespec ts; |
| |
| printf("%s", msg); |
| if (clock_gettime(cid, &ts) == \-1) |
| handle_error("clock_gettime"); |
| printf("%4ld.%03ld\en", ts.tv_sec, ts.tv_nsec / 1000000); |
| } |
| |
| int |
| main(int argc, char *argv[]) |
| { |
| pthread_t thread; |
| clockid_t cid; |
| int j, s; |
| |
| s = pthread_create(&thread, NULL, thread_start, NULL); |
| if (s != 0) |
| handle_error_en(s, "pthread_create"); |
| |
| printf("Main thread sleeping\en"); |
| sleep(1); |
| |
| printf("Main thread consuming some CPU time...\en"); |
| for (j = 0; j < 2000000; j++) |
| getppid(); |
| |
| pclock("Process total CPU time: ", CLOCK_PROCESS_CPUTIME_ID); |
| |
| s = pthread_getcpuclockid(pthread_self(), &cid); |
| if (s != 0) |
| handle_error_en(s, "pthread_getcpuclockid"); |
| pclock("Main thread CPU time: ", cid); |
| |
| /* The preceding 4 lines of code could have been replaced by: |
| pclock("Main thread CPU time: ", CLOCK_THREAD_CPUTIME_ID); */ |
| |
| s = pthread_getcpuclockid(thread, &cid); |
| if (s != 0) |
| handle_error_en(s, "pthread_getcpuclockid"); |
| pclock("Subthread CPU time: 1 ", cid); |
| |
| exit(EXIT_SUCCESS); /* Terminates both threads */ |
| } |
| .EE |
| .SH SEE ALSO |
| .BR clock_gettime (2), |
| .BR clock_settime (2), |
| .BR timer_create (2), |
| .BR clock_getcpuclockid (3), |
| .BR pthread_self (3), |
| .BR pthreads (7), |
| .BR time (7) |