The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.

#### NAME

> setreuid - set real and effective user IDs

#### SYNOPSIS

> ``[XSI] #include <unistd.h>
> int setreuid(uid_t` ruid`, uid_t` euid`);``
> `
> `

#### DESCRIPTION

> The setreuid() function shall set the real and effective user IDs of the current process to the values specified by the ruid and euid arguments. If ruid or euid is -1, the corresponding effective or real user ID of the current process shall be left unchanged.

> A process with appropriate privileges can set either ID to any value. An unprivileged process can only set the effective user ID if the euid argument is equal to either the real, effective, or saved user ID of the process.

> It is unspecified whether a process without appropriate privileges is permitted to change the real user ID to match the current real, effective, or saved set-user-ID of the process.

#### RETURN VALUE

> Upon successful completion, 0 shall be returned. Otherwise, -1 shall be returned and errno set to indicate the error.

#### ERRORS

> The setreuid() function shall fail if:

> [EINVAL]
>   The value of the ruid or euid argument is invalid or out-of-range.
> [EPERM]
>   The current process does not have appropriate privileges, and either an attempt was made to change the effective user ID to a value other than the real user ID or the saved set-user-ID or an attempt was made to change the real user ID to a value not permitted by the implementation.

The following sections are informative.

#### EXAMPLES

> ##### Setting the Effective User ID to the Real User ID

> The following example sets the effective user ID of the calling process to the real user ID, so that files created later will be owned by the current user.

>     #include <unistd.h>
>     #include <sys/types.h>
>     ...
>     setreuid(getuid(), getuid());
>     ...

#### APPLICATION USAGE

> None.

#### RATIONALE

> None.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> getegid(), geteuid(), getgid(), getuid(), setegid(), seteuid(), setgid(), setregid(), setuid(), the Base Definitions volume of IEEE Std 1003.1-2001, <unistd.h>

#### CHANGE HISTORY

> First released in Issue 4, Version 2.

#### Issue 5

> Moved from X/OPEN UNIX extension to BASE.

End of informative text.

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