Section: POSIX Programmer's Manual (3P)
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
--- get a real user ID
function shall return the real user ID of the calling process.
function shall not modify
function shall always be successful and no return value is reserved to
indicate the error.
No errors are defined.
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.
In a conforming environment,
will always succeed. It is possible for implementations to provide
an extension where a process in a non-conforming environment
will not be associated with a user or group ID. It is recommended
that such implementations return (uid_t
to indicate such an environment; doing so does not violate
this standard, since such an environment is already an extension.
The Base Definitions volume of POSIX.1-2017,
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 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 original Standard can be obtained online at
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