centos man page for seteuid

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

NAME
       seteuid, setegid - set effective user or group ID

SYNOPSIS
       #include <sys/types.h>
       #include <unistd.h>

       int seteuid(uid_t euid);
       int setegid(gid_t egid);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       seteuid(), setegid():
	   _BSD_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600

DESCRIPTION
       seteuid()  sets	the  effective user ID of the calling process.	Unprivileged user processes may only set the effective user ID to the real
       user ID, the effective user ID or the saved set-user-ID.

       Precisely the same holds for setegid() 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 seteuid(),  or  the	CAP_SETGID
	      capability  in  the case of setegid()) and euid (respectively, egid) is not the real user (group) ID, the effective user (group) ID,
	      or the saved set-user-ID (saved set-group-ID).

CONFORMING TO
       4.3BSD, POSIX.1-2001.

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).  On  an  arbi-
       trary system one should check _POSIX_SAVED_IDS.

       Under libc4, libc5 and glibc 2.0 seteuid(euid) is equivalent to setreuid(-1, euid) and hence may change the saved set-user-ID.  Under glibc
       2.1 and later it is equivalent to setresuid(-1, euid, -1) and hence does not change the saved  set-user-ID.   Analogous	remarks  hold  for
       setegid(),  with  the difference that the change in implementation from setregid(-1, egid) to setresgid(-1, egid, -1) occurred in glibc 2.2
       or 2.3 (dependeing on the hardware architecture).

       According to POSIX.1, seteuid() (setegid()) need not permit euid (egid) to be the same value as the current effective user (group) ID,  and
       some implementations do not permit this.

SEE ALSO
       geteuid(2), setresuid(2), setreuid(2), setuid(2), capabilities(7), credentials(7)

COLOPHON
       This  page is part of release 3.53 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								    2012-07-02								SETEUID(2)