seteuid(2)                                                   seteuid(2)

  setuid()

  NAME

    setuid(), seteuid(), setgid(), setegid(), - set user and group ID

  SYNOPSIS

    #include 
    #include 

    int setuid (uid_t uid)
    int seteuid (uid_t uid)
    int setgid (gid_t gid)
    int setegid (gid_t gid)

  DESCRIPTION

    The setuid(2) function sets the real and effective user IDs and the saved
    set-user-ID of the current process to the specified value. The setuid(2)
    function is permitted if the specified ID is equal to the real user ID of
    the process, or if the effective user ID has the appropriate privileges.

    The setgid(2) function sets the real and effective group IDs and the saved
    set-group-ID of the current process to the specified value. The setgid(2)
    function is permitted if the specified ID is equal to the real group ID of
    the process, or if the effective user ID has the appropriate privileges.

    For more details on security and appropriate permissions, see Security in
    the "Interix Overview" section of Windows Services for UNIX Help. Future
    releases of Window Services for UNIX may have a different implementation.

    The seteuid(2) function setegid(2) sets the effective user ID (group ID)
    of the current process. The effective user ID may be set to the value of
    the real user ID or the saved set-user-ID (see execve(2)); in this way,
    the effective user ID of a set-user-ID executable may be toggled by
    switching to the real user ID, then re-enabled by reverting to the set-
    user-ID value. Similarly, the effective group ID may be set to the value
    of the real group ID or the saved set-user-ID.

  RETURN VALUES

    Upon success, these functions return 0; otherwise -1 is returned.

    If the user is not the superuser, or the uid specified is not the real,
    effective ID, or saved ID, these functions return -1.

  ERRORS

    The setuid(2) and seteuid(2) functions can fail for the following reasons:

    [EINVAL]
        The value of the uid argument is invalid.

    [EPERM]
        The process does not have appropriate privileges and uid does not
        match the real user ID or the saved set-user-ID.

    The setegid(2) and setegid(2) functions can fail for the following
    reasons:

    [EINVAL]
        The value of the gid argument is invalid.

    [EPERM]
        The process does not have appropriate privileges and gid does not
        match the real group ID or the saved set-group-ID.

  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.

    By default, Interix does not execute files with the set-user-ID (setuid)
    or set-group-ID (setgid) mode bit set for security reasons. If an attempt
    is made to execute such a file, the ENOSETUID error is returned. For more
    information and and instructions for enabling execution of files with
    these mode bits set, see The superuser account and appropriate privileges
    in Windows Services for UNIX Help.

  SEE ALSO

    getuid(2)

    getgid(2)

  USAGE NOTES

    All of these functions are thread safe.

    The following functions are async-signal safe: setuid, setgid. The
    following functions are not async-signal safe: seteuid, setegid.