setuid, setruid, seteuid, or setreuid Subroutine

Base Operating System and Extensions Technical Reference, Volume 2

setuid, setruid, seteuid, or setreuid Subroutine

Purpose

Sets the process user IDs.

Library

Standard C Library (libc.a)

Syntax

#include <unistd.h>

int setuid (UID)
uid_t UID;

int setruid (RUID)
uid_t RUID;

int seteuid (EUID)
uid_t EUID;

int setreuid (RUID, EUID)
uid_t RUID;
uid_t EUID;

Description

The setuid, setruid, seteuid, and setreuid subroutines reset the process user IDs. The following semantics are supported:

setuid

If the effective user ID of the process is the root user, the process's real, effective, and saved user IDs are set to the value of the UID parameter. Otherwise, the process effective user ID is reset if the UID parameter specifies either the current real or saved user IDs.

seteuid

The process effective user ID is reset if the UID parameter is equal to either the current real or saved user IDs or if the effective user ID of the process is the root user.

setruid

The EPERM error code is always returned. Processes cannot reset only their real user IDs.

setreuid

The RUID and EUID parameters can have the following two possibilities:

RUID != EUID

If the EUID parameter specifies either the process's real or saved user IDs, the process effective user ID is set to the EUID parameter. Otherwise, the EPERM error code is returned.

RUID= = EUID

If the process effective user ID is the root user, the process's real and effective u ser IDs are set to the EUID parameter. Otherwise, the EPERM error code is returned.

The real and effective user ID parameters can have a value of -1. If the value is -1, the actual value for the UID parameter is set to the corresponding current the UID parameter of the process.

Parameters

UID	Specifies the user ID to set.
EUID	Specifies the effective user ID to set.
RUID	Specifies the real user ID to set.

Return Values

Upon successful completion, the setuid, seteuid, and setreuid subroutines return a value of 0. Otherwise, a value of -1 is returned and the errno global variable is set to indicate the error.

Error Codes

The setuid, seteuid, and setreuid subroutines are unsuccessful if either of the following is true:

EINVAL	The value of the UID or EUID parameter is not valid.
EPERM	The process does not have the appropriate privileges and the UID and EUID parameters are not equal to either the real or saved user IDs of the process.

Implementation Specifics

The operating system does not support setuid or setgid shell scripts.

These subroutines are part of Base Operating System (BOS) Runtime.

Related Information

The getuid or geteuid subroutine, setgid subroutine.

List of Security and Auditing Subroutines and Subroutines Overview in AIX Version 4.3 General Programming Concepts: Writing and Debugging Programs.