.\" Copyright (c) 2009 Linux Foundation, written by Michael Kerrisk .\" .\" .\" %%%LICENSE_START(VERBATIM) .\" Permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" Permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" Since the Linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. The author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. The author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" Formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%LICENSE_END .\" .TH PTHREAD_GETCPUCLOCKID 3 2020-11-01 "Linux" "Linux Programmer's Manual" .SH NAME pthread_getcpuclockid \- retrieve ID of a thread's CPU time clock .SH SYNOPSIS .nf .B #include .B #include .PP .BI "int pthread_getcpuclockid(pthread_t " thread ", clockid_t *" clockid ); .PP Compile and link with \fI\-pthread\fP. .fi .SH DESCRIPTION The .BR pthread_getcpuclockid () function obtains the ID of the CPU-time clock of the thread whose ID is given in .IR thread , and returns it in the location pointed to by .IR clockid . .\" 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 EXAMPLES 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 #include #include #include #include #include #include #include #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("%4jd.%03ld\en", (intmax_t) ts.tv_sec, ts.tv_nsec / 1000000); } int main(int argc, char *argv[]) { pthread_t thread; clockid_t cid; int 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 (int 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) .SH COLOPHON This page is part of release 5.10 of the Linux .I man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/.