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CLOCK_GETCPUCLOCKID(3) Linux Programmer's Manual CLOCK_GETCPUCLOCKID(3)

NAME

     clock_getcpuclockid - obtain ID of a process CPU-time clock

SYNOPSIS

     #include <time.h>

     int clock_getcpuclockid(pid_t pid, clockid_t *clock_id);

     Link with -lrt (only for glibc versions before 2.17).

 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  clock_id.   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
            obtaining the per-process CPU-time clock of another process.)

     ESRCH  There is no process with the ID pid.

VERSIONS

     The clock_getcpuclockid() function is available in glibc since  version
     2.2.

ATTRIBUTES

     For   an   explanation   of   the  terms  used  in  this  section,  see
     attributes(7).

     +----------------------+---------------+---------+
     |Interface             | Attribute     | Value   |
     +----------------------+---------------+---------+
     |clock_getcpuclockid() | Thread safety | MT-Safe |
     +----------------------+---------------+---------+

CONFORMING TO

     POSIX.1-2001, POSIX.1-2008.

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.

EXAMPLE

     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  <stdio.h>  #include  <unistd.h>
     #include <stdlib.h> #include <time.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 %ld.%09ld seconds\n",
                 argv[1], (long) ts.tv_sec, (long) ts.tv_nsec);
         exit(EXIT_SUCCESS); }