---
name: "clock_getcpuclockid"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/clock_getcpuclockid"
---

# clock\_getcpuclockid(3)

obtain ID of a process CPU-time clock

## 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)](/feature_test_macros/7.md)):

**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 obtaining 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)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **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)](/clock_gettime/2.md) 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)](/clock_gettime/2.md) 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)](/clock_getres/2.md), [**timer\_create**(2)](/timer_create/2.md), [**pthread\_getcpuclockid**(3)](/pthread_getcpuclockid/3.md), [**time**(7)](/time/7.md)