SETREUID(2)SETREUID(2)NAMEsetreuid - set real and effective user IDs
SYNOPSIS
#include <unistd.h>
int setreuid(uid_t ruid, uid_t euid);
DESCRIPTION
The setreuid() function is used to set the real and effective user IDs
of the calling process. If ruid is −1, the real user ID is not changed;
if euid is −1, the effective user ID is not changed. The real and
effective user IDs may be set to different values in the same call.
If the {PRIV_PROC_SETID} privilege is asserted in the effective set of
the calling process, the real user ID and the effective user ID can be
set to any legal value.
If the {PRIV_PROC_SETID} privilege is not asserted in the effective set
of the calling process, either the real user ID can be set to the
effective user ID, or the effective user ID can either be set to the
saved set-user ID from execve() (seeexec(2)) or the real user ID.
In either case, if the real user ID is being changed (that is, if ruid
is not −1), or the effective user ID is being changed to a value not
equal to the real user ID, the saved set-user ID is set equal to the
new effective user ID.
All privileges are required to change to uid 0.
RETURN VALUES
Upon successful completion, 0 is returned. Otherwise, −1 is returned,
errno is set to indicate the error, and neither of the user IDs will be
changed.
ERRORS
The setreuid() function will fail if:
EINVAL
The value of ruid or euid is less than 0 or greater than
UID_MAX (defined in <limits.h>).
EPERM
The {PRIV_PROC_SETID} privilege is not asserted in the effec‐
tive set of the calling processes and a change was specified
other than changing the real user ID to the effective user
ID, or changing the effective user ID to the real user ID or
the saved set-user ID. See privileges(5) for additional
restrictions which apply when changing to UID 0.
USAGE
If a set-user-ID process sets its effective user ID to its real user
ID, it can still set its effective user ID back to the saved set-user
ID.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌────────────────────┬─────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼─────────────────┤
│Interface Stability │ Standard │
└────────────────────┴─────────────────┘
SEE ALSOexec(2), getuid(2), setregid(2), setuid(2), attributes(5), privi‐
leges(5), standards(5)
Mar 22, 2004 SETREUID(2)
