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  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.   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

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