clock_getcpuclockid(3) - Man pages

clock_getcpuclockid(3)      Library Functions Manual     clock_getcpuclockid(3)

NAME
       clock_getcpuclockid - obtain ID of a process CPU-time clock

LIBRARY
       Standard C library (libc, -lc), since glibc 2.17

       Before glibc 2.17, Real-time library (librt, -lrt)

SYNOPSIS
       #include <time.h>

       int clock_getcpuclockid(pid_t pid, clockid_t *clockid);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       clock_getcpuclockid():
           _POSIX_C_SOURCE >= 200112L

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

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

ERRORS
       ENOSYS The  kernel  does  not support obtaining the per-process CPU-time
              clock of another process, and pid does not  specify  the  calling
              process.

       EPERM  The  caller does not have permission to access the CPU-time clock
              of the process specified by  pid.   (Specified  in  POSIX.1-2001;
              does  not  occur  on Linux unless the kernel does not support ob-
              taining the per-process CPU-time clock of another process.)

       ESRCH  There is no process with the ID pid.

ATTRIBUTES
       For an explanation of the terms used in this section, see attributes(7).
       ┌────────────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                                  │ Attribute     │ Value   │
       ├────────────────────────────────────────────┼───────────────┼─────────┤
       │ clock_getcpuclockid()                      │ Thread safety │ MT-Safe │
       └────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS
       POSIX.1-2008.

HISTORY
       glibc 2.2.  POSIX.1-2001.

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

EXAMPLES
       The  example  program below obtains the CPU-time clock ID of the process
       whose ID is given on the command line, and then uses clock_gettime(2) to
       obtain the time on that clock.  An example run is the following:

           $ ./a.out 1                 # Show CPU clock of init process
           CPU-time clock for PID 1 is 2.213466748 seconds

   Program source

       #define _XOPEN_SOURCE 600
       #include <stdint.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <time.h>
       #include <unistd.h>

       int
       main(int argc, char *argv[])
       {
           clockid_t clockid;
           struct timespec ts;

           if (argc != 2) {
               fprintf(stderr, "%s <process-ID>\n", argv[0]);
               exit(EXIT_FAILURE);
           }

           if (clock_getcpuclockid(atoi(argv[1]), &clockid) != 0) {
               perror("clock_getcpuclockid");
               exit(EXIT_FAILURE);
           }

           if (clock_gettime(clockid, &ts) == -1) {
               perror("clock_gettime");
               exit(EXIT_FAILURE);
           }

           printf("CPU-time clock for PID %s is %jd.%09ld seconds\n",
                  argv[1], (intmax_t) ts.tv_sec, ts.tv_nsec);
           exit(EXIT_SUCCESS);
       }

SEE ALSO
       clock_getres(2), timer_create(2), pthread_getcpuclockid(3), time(7)

Linux man-pages 6.9.1              2024-06-15            clock_getcpuclockid(3)

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