I think the CASE LEN( CHRTRAN( m.lcUpperJustFileName, m.lcValidChars, "" ) ) > 0 catches this.

>>>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.
>
>>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 
>>