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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.  Unprivi-
       leged 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.

       Note: there are cases where seteuid() can fail even when	the caller  is
       UID  0; it is a grave security error to omit checking for a failure re-
       turn from seteuid().

ERRORS
       EINVAL The target user or group ID is not valid in this user namespace.

       EPERM  The calling process is not privileged (Linux: does not have  the
	      CAP_SETUID  capability in	the case of seteuid(), or the CAP_SET-
	      GID 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 arbitrary
       system one should check _POSIX_SAVED_IDS.

       Under 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 dif-
       ference that the	change in implementation from  setregid(-1,  egid)  to
       setresgid(-1,  egid, -1)	occurred in glibc 2.2 or 2.3 (depending	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.

   C library/kernel ABI	differences
       On Linux, seteuid() and setegid() are implemented as library  functions
       that call, respectively,	setreuid(2) and	setresgid(2).

SEE ALSO
       geteuid(2), setresuid(2), setreuid(2), setuid(2), capabilities(7), cre-
       dentials(7), user_namespaces(7)

COLOPHON
       This page is part of release 3.74 of the	Linux  man-pages  project.   A
       description  of	the project, information about reporting bugs, and the
       latest	 version    of	  this	  page,	   can	   be	  found	    at
       http://www.kernel.org/doc/man-pages/.

Linux				  2014-09-21			    SETEUID(2)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

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