RTOS/am3359: How to achieve TI-RTOS MMCSD FATFS full function ?

Tool/software: TI-RTOS

Hi TI,

                   ccs 7.2.0, ti-processor-sdk-rtos-am335x-evm-04.00.00.04, am335x starter kit

I am working on the example project MMCSD_FatfsConsole_skAM335x_armExampleProject from pdk_am335x_1_0_7.

According to processors.wiki.ti.com/.../Processor_SDK_RTOS_MMCSD.

Console commands supported are ls (to list files of directory), cd (change directory), pwd (present working directory) and cat (text file read operation).

I am wondering how to realize the full filesystem functionality, especially writing to a file, such as

echo "Some text here." > myfile.txt.

or

cat > outfile.txt
>Enter text
>to save press ctrl-d

Please advise, thanks in advance.

Mike