SETREUID(P) POSIX Programmer's Manual SETREUID(P)
setreuid - set real and effective user IDs
int setreuid(uid_t ruid, uid_t euid);
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 corre-
sponding 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
Upon successful completion, 0 shall be returned. Otherwise, -1 shall be returned and errno
set to indicate the error.
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.
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.
getegid() , geteuid() , getgid() , getuid() , setegid() , seteuid() , setgid() ,
setregid() , setuid() , the Base Definitions volume of IEEE Std 1003.1-2001, <unistd.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 SETREUID(P)