getuid() -- System Call (libc)

Get real user identifier
#include <unistd.h>
int getuid()

Every process  has two different versions  of its user id,  called the real
user id and  the effective user id.  The user  ids determine eligibility to
access  files or  employ system  privileges.  Normally,  these two  ids are
identical.  However, for  a set user id load module  (see exec()), the real
user id is  that of the user, whereas the  effective user id is that of the
load module  owner.  This distinction  allows system programs  to use files
which are protected from the user who invokes the program.

getuid() returns the real user id.

Example

For an example of this call, see the entry for getpwent().

See Also

access(),
exec,
getegid(),
geteuid(),
getgid(),
libc,
login,
setuid(),
unistd.h
POSIX Standard, §4.2.1

© 2012 by Stephen A. Ness