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setreuid(2) [netbsd 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

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SETREUID(2)						     Linux Programmer's Manual						       SETREUID(2)

NAME
setreuid, setregid - set real and/or effective user or group ID SYNOPSIS
#include <sys/types.h> #include <unistd.h> int setreuid(uid_t ruid, uid_t euid); int setregid(gid_t rgid, gid_t egid); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): setreuid(), setregid(): _BSD_SOURCE || _XOPEN_SOURCE >= 500 DESCRIPTION
setreuid() sets real and effective user IDs of the calling process. Supplying a value of -1 for either the real or effective user ID forces the system to leave that ID unchanged. Unprivileged processes may only set the effective user ID to the real user ID, the effective user ID, or the saved set-user-ID. Unprivileged users may only set the real user ID to the real user ID or the effective user ID. If the real user ID is set or the effective user ID is set to a value not equal to the previous real user ID, the saved set-user-ID will be set to the new effective user ID. Completely analogously, setregid() sets real and effective group ID's of the calling process, and all of the above holds with "group" instead of "user". RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is set appropriately. ERRORS
EPERM The calling process is not privileged (Linux: does not have the CAP_SETUID capability in the case of setreuid(), or the CAP_SETGID capability in the case of setregid()) and a change other than (i) swapping the effective user (group) ID with the real user (group) ID, or (ii) setting one to the value of the other or (iii) setting the effective user (group) ID to the value of the saved set-user- ID (saved set-group-ID) was specified. CONFORMING TO
POSIX.1-2001, 4.3BSD (the setreuid() and setregid() function calls first appeared in 4.2BSD). NOTES
Setting the effective user (group) ID to the saved set-user-ID (saved set-group-ID) is possible since Linux 1.1.37 (1.1.38). POSIX.1 does not specify all of possible ID changes that are permitted on Linux for an unprivileged process. For setreuid(), the effective user ID can be made the same as the real user ID or the save set-user-ID, and it is unspecified whether unprivileged processes may set the real user ID to the real user ID, the effective user ID, or the saved set-user-ID. For setregid(), the real group ID can be changed to the value of the saved set-group-ID, and the effective group ID can be changed to the value of the real group ID or the saved set-group-ID. The precise details of what ID changes are permitted vary across implementations. POSIX.1 makes no specification about the effect of these calls on the saved set-user-ID and saved set-group-ID. SEE ALSO
getgid(2), getuid(2), seteuid(2), setgid(2), setresuid(2), setuid(2), capabilities(7) COLOPHON
This page is part of release 3.25 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2009-10-17 SETREUID(2)

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