clock_getcpuclockid(3)

1CLOCK_GETCPUCLOCKID(3)     Linux Programmer's Manual    CLOCK_GETCPUCLOCKID(3)
2
3
4

NAME

6       clock_getcpuclockid - obtain ID of a process CPU-time clock
7

SYNOPSIS

9       #include <time.h>
10
11       int clock_getcpuclockid(pid_t pid, clockid_t *clock_id);
12
13       Link with -lrt (only for glibc versions before 2.17).
14
15   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
16
17       clock_getcpuclockid():
18           _POSIX_C_SOURCE >= 200112L
19

DESCRIPTION

21       The clock_getcpuclockid() function obtains the ID of the CPU-time clock
22       of the process whose ID is pid, and returns it in the location  pointed
23       to  by  clock_id.   If  pid  is zero, then the clock ID of the CPU-time
24       clock of the calling process is returned.
25

RETURN VALUE

27       On success, clock_getcpuclockid() returns 0; on error, it  returns  one
28       of the positive error numbers listed in ERRORS.
29

ERRORS

31       ENOSYS The  kernel  does not support obtaining the per-process CPU-time
32              clock of another process, and pid does not specify  the  calling
33              process.
34
35       EPERM  The caller does not have permission to access the CPU-time clock
36              of the process specified by pid.   (Specified  in  POSIX.1-2001;
37              does  not  occur  on  Linux  unless  the kernel does not support
38              obtaining the per-process CPU-time clock of another process.)
39
40       ESRCH  There is no process with the ID pid.
41

VERSIONS

43       The clock_getcpuclockid() function is available in glibc since  version
44       2.2.
45

ATTRIBUTES

47       For   an   explanation   of   the  terms  used  in  this  section,  see
48       attributes(7).
49
50       ┌──────────────────────┬───────────────┬─────────┐
51       │Interface             │ Attribute     │ Value   │
52       ├──────────────────────┼───────────────┼─────────┤
53       │clock_getcpuclockid() │ Thread safety │ MT-Safe │
54       └──────────────────────┴───────────────┴─────────┘

CONFORMING TO

56       POSIX.1-2001, POSIX.1-2008.
57

NOTES

59       Calling clock_gettime(2) with the  clock  ID  obtained  by  a  call  to
60       clock_getcpuclockid()  with  a pid of 0, is the same as using the clock
61       ID CLOCK_PROCESS_CPUTIME_ID.
62

EXAMPLE

64       The example program below obtains the CPU-time clock ID of the  process
65       whose  ID  is given on the command line, and then uses clock_gettime(2)
66       to obtain the time on that clock.  An example run is the following:
67
68           $ ./a.out 1                 # Show CPU clock of init process
69           CPU-time clock for PID 1 is 2.213466748 seconds
70
71   Program source
72
73       #define _XOPEN_SOURCE 600
74       #include <stdio.h>
75       #include <unistd.h>
76       #include <stdlib.h>
77       #include <time.h>
78
79       int
80       main(int argc, char *argv[])
81       {
82           clockid_t clockid;
83           struct timespec ts;
84
85           if (argc != 2) {
86               fprintf(stderr, "%s <process-ID>\n", argv[0]);
87               exit(EXIT_FAILURE);
88           }
89
90           if (clock_getcpuclockid(atoi(argv[1]), &clockid) != 0) {
91               perror("clock_getcpuclockid");
92               exit(EXIT_FAILURE);
93           }
94
95           if (clock_gettime(clockid, &ts) == -1) {
96               perror("clock_gettime");
97               exit(EXIT_FAILURE);
98           }
99
100           printf("CPU-time clock for PID %s is %ld.%09ld seconds\n",
101                   argv[1], (long) ts.tv_sec, (long) ts.tv_nsec);
102           exit(EXIT_SUCCESS);
103       }
104

COLOPHON

109       This page is part of release 4.16 of the Linux  man-pages  project.   A
110       description  of  the project, information about reporting bugs, and the
111       latest    version    of    this    page,    can     be     found     at
112       https://www.kernel.org/doc/man-pages/.
113
114
115
116Linux                             2017-09-15            CLOCK_GETCPUCLOCKID(3)