If you enable verbose output in the Arduino IDE (file->preferences->show verbose output during output)
You can see which parameters Arduino use:
D:\arduino-1.01\arduino-1.0.1-windows (1)\arduino-1.0.1\hardware/tools/avr/bin/avrdude -CD:\arduino-1.01\arduino-1.0.1-windows (1)\arduino-1.0.1\hardware/tools/avr/etc/avrdude.conf -v -v -v -v -patmega328p -carduino -P\\.\COM20 -b115200 -D -Uflash:w:C:\Users\EC\AppData\Local\Temp\build3006186476715730111.tmp\Blink.cpp.hex:i
In my example i had just renamed the Blink.cpp.hex.
Also note the -v options. It enables verbose output, and will show error messages etc.