setreuid()

Updated: May 06, 2022

Set the real and effective user IDs for the calling process

Synopsis:

#include <unistd.h>

int setreuid( uit_t ruid, 
              uid_t euid );

Arguments:

ruid
The real user ID that you want to use for the process, or -1 if you don't want to change it.
euid
The effective user ID that you want to use for the process, or -1 if you don't want to change it.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The setreuid() function lets the calling process set its real and effective user IDs to its real or effective user ID, its saved set-user ID, or to any of the user IDs identified by the PROCMGR_AID_SETUID ability (see procmgr_ability()). If ruid or euid is -1, the corresponding real or effective user ID isn't changed.

Note: If a set-UID process sets its effective user ID to its real user ID, it can still set its effective user ID back to the saved set-UID.

In either case, if you're changing the real user ID (i.e., ruid isn't -1), or you're changing the effective user ID to a value that isn't equal to the real user ID, the saved set-user ID is set equal to the new effective user ID.

QNX recommends that you do not use a negative value for a user ID.

Returns:

Zero on success, or -1 if an error occurs (errno is set).

Errors:

EINVAL
The ruid or euid is out of range.
EPERM
The calling process doesn't have the PROCMGR_AID_SETUID ability enabled, and you tried to change the effective user ID to a value other than the real or saved set-user ID.

Or:

The calling process doesn't have the PROCMGR_AID_SETUID ability enabled, and you tried to change the real user ID to a value other than the effective user ID.

Classification:

POSIX 1003.1

Safety:  
Cancellation point No
Interrupt handler No
Signal handler Yes
Thread Yes