---
name: "geteuid"
section: "2"
platform: "macos"
package: "xnu"
version: "12377.121.6"
release: "macOS 26.5"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/getuid"
---

# geteuid(2)

get user identification

Part of [getuid(2)](/getuid/2.md).

## NAME

**geteuid**, **getuid** – get user identification

## SYNOPSIS

**#include \<unistd.h\>**

*uid\_t*\

**geteuid**(*void*);

*uid\_t*\

**getuid**(*void*);

## DESCRIPTION

The **getuid**() function returns the real user ID of the calling process. The **geteuid**() function returns the effective user ID of the calling process.

The real user ID is that of the user who has invoked the program. As the effective user ID gives the process additional permissions during execution of “*set-user-ID*” mode processes, **getuid**() is used to determine the real-user-id of the calling process.

## ERRORS

The **getuid**() and **geteuid**() functions are always successful, and no return value is reserved to indicate an error.

## LEGACY SYNOPSIS

**#include \<sys/types.h\>** **#include \<unistd.h\>**

The include file ⟨sys/types.h⟩ is necessary for both functions.

## SEE ALSO

[getgid(2)](/getgid/2.md), [setreuid(2)](/setreuid/2.md), [compat(5)](/compat/5.md)

## STANDARDS

**geteuid**() and **getuid**() functions conform to IEEE Std 1003.1-1988 (“POSIX.1”).