And of course there is the remote possibility of serial (COM#) and parallel ports (LPT#) extending to more than the default number (e.g. I've run into situation where there was a COM25 serial port)...

>>>I have a backup menu dan the client can create his own backup filename.
>
>I think NUL is missing from the list of no-nos.

Of course one could claim that if you name your backup NUL, the backup will require ABSOLUTELY NO DISK SPACE!
(of course the minor downside is that you won't be able to retrieve anything from such a backup...)

>
>>This is what we use, is was from Chris Lange I think
>>

>>********************************************************************
>>FUNCTION lValidFileName( tcFileName )
>>********************************************************************
>>  LOCAL lcValidChars, lcUpperJustFileName
>>
>>  m.lcValidChars        = " ^'@{}[],=()+._-!$%&/#~1234567890ABCEDFGHIJKLMONPQRSTUVWXYZ"
>>  m.lcUpperJustFileName = UPPER( JUSTFNAME(m.tcFileName) )
>>
>>    DO CASE
>>	CASE EMPTY( m.lcUpperJustFileName )
>>		RETURN .F.
>>	CASE INLIST( JUSTSTEM(m.lcUpperJustFileName), "AUX", "COM1", "COM2", "COM3", "COM4", "CON", "LPT1", "PRN" ) 
>>		RETURN .F.
>>	CASE LEN( CHRTRAN( m.lcUpperJustFileName, m.lcValidChars, "" ) ) > 0
>>		RETURN .F.
>>	OTHERWISE
>>		RETURN .T.
>>    ENDCASE
>>
>>ENDFUNC 
>>