Copyright (C) 2001 Andries Brouwer (firstname.lastname@example.org) %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the L...
NAMEseteuid, setegid - set effective user or group ID
int seteuid(uid_t euid);
int setegid(gid_t egid);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
- _BSD_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600
DESCRIPTIONseteuid() 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 VALUEOn 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().
- The target user or group ID is not valid in this user namespace.
- 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 TOPOSIX.1-2001, POSIX.1-2008, 4.3BSD.
NOTESSetting 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
is equivalent to
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
with the difference that the change in implementation from
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.