NAME

getuid — get a real user ID

SYNOPSIS

#include <unistd.h>

uid_t getuid(void);


DESCRIPTION

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

RETURN VALUE

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

ERRORS

No errors are defined.

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.

#include <unistd.h>
...
seteuid(getuid());

APPLICATION USAGE

None.

RATIONALE

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.

FUTURE DIRECTIONS

None.

SEE ALSO

getegid, geteuid, getgid, getresgid, getresuid, setegid, seteuid, setgid, setregid, setresgid, setresuid, setreuid, setuid

XBD <sys/types.h>, <unistd.h>

CHANGE HISTORY

First released in Issue 1. Derived from Issue 1 of the SVID.

Issue 6

In the SYNOPSIS, the optional include of the <sys/types.h> header is removed.

The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:

• The requirement to include <sys/types.h> has been removed. Although <sys/types.h> was required for conforming implementations of previous POSIX specifications, it was not required for UNIX applications.

Issue 7

POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0175 [511] and XSH/TC2-2008/0176 [897] are applied.

Issue 8

Austin Group Defect 1344 is applied, adding getresgid(), getresuid(), setresgid(), and setresuid() to SEE ALSO.