setreuid(2) System Calls Manual setreuid(2)Name
setreuid - set real and effective user ID's
Syntax
setreuid(ruid, euid)
intruid, euid;
Description
The real and effective user ID's of the current process are set according to the arguments. If ruid or euid is -1, the current uid is
filled in by the system.
Return Values
Upon successful completion, a value of zero (0) is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.
Environment
BSD
If the process is superuser, or and matches with the real user ID, the effective user ID, or the saved set-user-id (as described in ), then
the real, effective, and the saved set-user-id are set to and respectively.
POSIX
SYSTEM-FIVE
When your program is compiled in the POSIX or SYSTEM-FIVE mode, if both arguments to are -1, the system call returns a value of -1 and
errno is set to [EINVAL].
The following semantics apply when using the function:
If the process is the superuser, the real, effective, and saved set-user-id (as described in ) are set to and respectively.
If the process is not the superuser, but the and matches with the real user ID, the effective user ID (only in the SYSTEM-FIVE and BSD
environments), or the saved set-user-id, then the effective ID is set to The real user ID and the saved set-user-id are left unchanged.
Diagnostics
[EPERM] The current process is not the superuser and the and specified does not match with the real user ID, the effective user ID
(only in SYSTEM-FIVE and BSD environment), or the saved set-user-id.
See Alsogetuid(2), setregid(2), setuid(3)setreuid(2)
Check Out this Related Man Page
SETREUID(2) BSD System Calls Manual SETREUID(2)NAME
setreuid -- set real and effective user ID's
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <unistd.h>
int
setreuid(uid_t ruid, uid_t euid);
DESCRIPTION
This interface is made obsolete by the saved ID functionality in setuid(2) and seteuid(2).
The real and effective user ID's of the current process are set according to the arguments. If the real user ID is changed, the saved user
ID is changed to the new value of the effective user ID.
If ruid or euid is -1, the current uid is filled in by the system. Unprivileged users may change the real user ID to the effective user ID,
and may change the effective user ID to the real user ID or the saved user ID; only the super-user may make other changes.
The setreuid() function has been used to swap the real and effective user IDs in set-user-ID programs to temporarily relinquish the set-user-
ID value. This purpose is now better served by the use of the seteuid() function (see setuid(2)).
When setting the real and effective user IDs to the same value, this function is equivalent to the setuid() function. When setting only the
effective user ID, this function is equivalent to the seteuid() function.
RETURN VALUES
Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.
ERRORS
[EPERM] The current process is not the super-user and a change other than changing the effective user-id to the real user-id was
specified.
SEE ALSO getuid(2), seteuid(2), setgid(2), setuid(2)HISTORY
The setreuid() function call appeared in 4.2BSD. An incompatible version was implemented in 4.4BSD. It was reimplemented in NetBSD 1.2 in a
way compatible with 4.3BSD, SunOS and Linux, but should not be used in new code.
BSD January 5, 2001 BSD
I know that in order to get a real user name I should use the following command: cut -d: -f5 /etc/passwd. But how can I get the real user name for those users who are currently logged in to the system??? :confused: Can somebody help me??? (3 Replies)
I would like to know the difference between the real user-id and the
effective user-id. If user-A runs a program owned by user-B then
which is the real user-id and which is the effective user-id ? (1 Reply)
Write a tool that will be displayed in real time, what user connects or disconnects from a system that uses this tool :))
Maybe anyone can help me? (2 Replies)
Hi all,
Ok, bear with me on this one, I am a bit new to Unix and it might take me a little bit of time to articulate my question.
I know that every process has a user id and an effective user id. This seems to include the shell itself, because when I type 'ps', I see 'bash' listed as a... (2 Replies)
Hello all.
Despite the exec man page, the exec system call seems to turn my effective-user-id into my real-user-id.
I coded and compiled 2 very simple c programs as user 1 (uid=501)
The first one (A) prints real and effective user IDs and then execs the second one (B), which in turn prints... (7 Replies)