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);
DESCRIPTION
seteuid sets the effective user ID of the current process. Unprivileged user processes may only set the effective user ID to the real user
ID, the effective user ID or the saved 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 current process is not the super-user and euid (resp. egid) is not the real user (group) ID, the effective user (group) ID or
the saved user (group) ID.
NOTES
Setting the effective user (group) ID to the saved user (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 glibc2.0 seteuid(euid) is equivalent to setreuid(-1, euid) and hence may change the saved user ID. Under glibc2.1
it is equivalent to setresuid(-1, euid,-1) and hence does not change the saved user ID. Similar remarks hold for setegid.
CONFORMING TO
BSD 4.3
SEE ALSO
geteuid(2), setuid(2), setreuid(2), setresuid(2)
Linux 2.4 2001-05-17 SETEUID(2)