NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | NOTES | EXAMPLES | SEE ALSO | COLOPHON |
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clock_getcpuclockid(3) Library Functions Manual clock_getcpuclockid(3)
clock_getcpuclockid - obtain ID of a process CPU-time clock
Standard C library (libc, -lc), since glibc 2.17 Before glibc 2.17, Real-time library (librt, -lrt)
#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
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.
On success, clock_getcpuclockid() returns 0; on error, it returns one of the positive error numbers listed in 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.
For an explanation of the terms used in this section, see attributes(7). ┌─────────────────────────────────────┬───────────────┬─────────┐ │ Interface │ Attribute │ Value │ ├─────────────────────────────────────┼───────────────┼─────────┤ │ clock_getcpuclockid() │ Thread safety │ MT-Safe │ └─────────────────────────────────────┴───────────────┴─────────┘
POSIX.1-2008.
glibc 2.2. POSIX.1-2001.
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.
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); }
clock_getres(2), timer_create(2), pthread_getcpuclockid(3), time(7)
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Linux man-pages 6.9.1 2024-06-15 clock_getcpuclockid(3)
Pages that refer to this page: clock_getres(2), clock_nanosleep(2), timer_create(2), clockid_t(3type), pthread_getcpuclockid(3), time(7)