limtRead for os.reboot()

function limitRead( nLength, cReplaceChar )
    term.setCursorBlink( true )

    nLength = nLength or -1 -- -1 is unlimited
    sReturnString = ""

    xPos, yPos = term.getCursorPos()

    while true do
        event, char = os.pullEvent()

        if nLength ~= -1 and string.len( sReturnString ) >= nLength then term.setCursorBlink( false ); return sReturnString end -- Length check

        if event == "char" then sReturnString = sReturnString .. char
        elseif event == "key" and char == 28 then term.setCursorBlink( false ); return sReturnString -- Enter
        elseif event == "key" and char == 14 then -- Backspace
            term.setCursorPos( xPos, yPos )
            term.write( string.rep( " ", string.len( sReturnString ) ) )
            sReturnString = string.sub( sReturnString, 1, string.len( sReturnString )-1 )
            term.setCursorPos( xPos, yPos )

            if not cReplaceChar then term.write( sReturnString )
            else term.write( string.rep( cReplaceChar, string.len( sReturnString ) ) ) end
        end

        term.setCursorPos( xPos, yPos )
        term.write( string.rep( " ", string.len( sReturnString ) ) )
        term.setCursorPos( xPos, yPos )
        if not cReplaceChar then term.write( sReturnString )
        else term.write( string.rep( cReplaceChar, string.len( sReturnString ) ) ) end
    end
end