Variable doesnt take Value ?

Projects Programming
1 
String Test;
Serial.println("Datum: " + S_Datum);
if (S_Datum != "" & S_Datum.length() == 6) {
    Test = S_Datum + ".gpx";
    Serial.println(Test);
    Test.toCharArray(DATEINAME_CHAR,11);
    Serial.println(DATEINAME_CHAR);
........

S_Datum = String...
S_Datum got value....

Problem: Serial.println(Text) is empty ?!?

2 
(S_Datum != "" & S_Datum.length() == 6)

The single & is a binary and operation, not a logical and. It is a good idea to use parentheses to separate clauses in your if statements.

3

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