GETUID(3P) POSIX Programmer's Manual GETUID(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.

getuid — get a real user ID

#include <unistd.h>
uid_t getuid(void);

The getuid() function shall return the real user ID of the calling process. The getuid() function shall not modify errno.

The getuid() function shall always be successful and no return value is reserved to indicate the error.

No errors are defined.

The following sections are informative.

The following example sets the effective user ID of the calling process to the real user ID.

#include <unistd.h>


In a conforming environment, getuid() 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)-1 and set errno to indicate such an environment; doing so does not violate this standard, since such an environment is already an extension.


getegid(), geteuid(), getgid(), setegid(), seteuid(), setgid(), setregid(), setreuid(), setuid()

The Base Definitions volume of POSIX.1‐2017, <sys_types.h>, <unistd.h>

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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2017 IEEE/The Open Group