setegid

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
       return 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
       POSIX.1-2001, POSIX.1-2008, 4.3BSD.

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 differences
       On Linux, seteuid() and setegid() are implemented as library  functions
       that call, respectively, setreuid(2) and setregid(2).

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

COLOPHON
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       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                             2015-07-23                        SETEUID(2)
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