setreuid(2)                                                 setreuid(2)

  setreuid()

  NAME

    setreuid() - set real and effective user ID's

  SYNOPSIS

    #include 

    int setreuid (uid_t ruid, uid_t euid)

  DESCRIPTION

    The real and effective user IDs of the current process are set according
    to the arguments. If ruid or euid is -1, the current uid is filled in by
    the system. Unprivileged users may change the real user ID to the
    effective user ID and vice-versa; only the superuser may make other
    changes.

    The setreuid(2) function has been used to swap the real and effective user
    IDs in set-user-ID programs to temporarily relinquish the set-user-ID
    value. This purpose is now better served by the use of the seteuid(2)
    function (see setuid(2)).

    When setting the real and effective user IDs to the same value, the
    standard setuid(2) function is preferred.

  RETURN VALUES

    Upon successful completion, a value of 0 is returned. Otherwise, a value
    of -1 is returned and errno is set to indicate the error.

  ERRORS

    The setreuid(2) call can fail for the following reasons:

    [EPERM]
        The current process is not the superuser and a change other than
        changing the effective user-id to the real user-id was specified.

  NOTES

    The appropriate privileges are granted to the following users: The SYSTEM
    account, the Administrator account of the principal domain, and the
    Administrator account of the local domain.

    The local Administrator account is restricted to setting the UID to local
    accounts.

  SEE ALSO

    getuid(2)

    seteuid(2)

    setuid(2)

  USAGE NOTES

    The setreuid function is thread safe.

    The setreuid function is not async-signal safe.