Section (2) seteuid
seteuid, setegid — set effective user or group ID
#include <sys/types.h> #include <unistd.h>
seteuid() sets the effective
user ID of the calling process. Unprivileged 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
On success, zero is returned. On error, −1 is
errno is set
there are cases where
The target user or group ID is not valid in this user namespace.
In the case of
seteuid(): the calling process is not privileged (does not have the
CAP_SETUIDcapability in its user namespace) and
euiddoes not match the current real user ID, current effective user ID, or current saved set-user-ID.
In the case of
setegid(): the calling process is not privileged (does not have the
CAP_SETGIDcapability in its user namespace) and
egiddoes not match the current real group ID, current effective group ID, or current saved set-group-ID.
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
Under glibc 2.0,
euid) is equivalent to
euid) and hence may change the
saved set-user-ID. Under glibc 2.1 and later, it is
−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
−1) occurred in glibc 2.2
or 2.3 (depending on the hardware architecture).
According to POSIX.1,
setegid()) need not permit
egid) to be the same value as
the current effective user (group) ID, and some
implementations do not permit this.
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Copyright (C) 2001 Andries Brouwer (aebcwi.nl)
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[should really be seteuid.3]
Modified, 27 May 2004, Michael Kerrisk <mtk.manpagesgmail.com>
Added notes on capability requirements