Mbedflsh error code 1

I use mbedflsh to flash config files to the device.
Specifically, if i type

mbedflsh -f identRev.txt -d /run/media/ernst/MBED

identRev.txt being an existing file and /run/media/ernst/MBED the mount point of my LPC1768,
that file is correctly flashed.
Also I can see output mbedflsh: opening file identRev.txt...

BUT: error code seems to be 1 and i miss another message
as the first seems to indicate only the beginning of the action.

I use os 5.15.

Another question: why is it better to use mbedflsh than to just copy.
Also -c seems to be the flash method… if i do cp is it just copy???
but this would depend on the OS right?