seteuid

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.

ERRORS
       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  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.  Similar remarks hold  for
       setegid().

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

COLOPHON
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