public void setCommandAppendOperator(String commandAppendOperator) {
        this.commandAppendOperator = commandAppendOperator;
    }
Sets the operator to append rather than replace a value for the command
line tool, i.e. "+=".

@param commandAppendOperator
tika-core/src/main/java/org/apache/tika/embedder/ExternalEmbedder.java