The idea to monitor and communicate with the device is the same on both OS, what changes is the device name. For Linux the devices name to use can be found with
sudo dmesg | grep tty
Normally is/dev/ttyUSB0, /dev/ttyUSB1, /dev/ttyUSB2, /dev/ttyUSB3, /dev/ttyUSB4 for Linux, and on my Mac osX Lion I have
ls -l /dev/cu.* crw-rw-rw- 1 root wheel /dev/cu.HUAWEIMobile-Diag crw-rw-rw- 1 root wheel /dev/cu.HUAWEIMobile-Modem crw-rw-rw- 1 root wheel /dev/cu.HUAWEIMobile-Pcui
For this purpose lets assume a generic device name <DEVICE>, that it is either a Linux or osX tty. First we need to find out which of the several terminal is used for communication, and for that we need to open monitor terminals for each of the devices.
Terminal 1: cat /dev/<DEVICE1>
Terminal 2: cat /dev/<DEVICE2>
and in another terminal we send an AT command like this:
echo "ATi^M" > /dev/<DEVICE> #(note: ^M is ctrl+v+m)
And one of the monitor terminals above will show something like this:
ATi Manufacturer: huawei Model: E353 Revision: 11.810.09.40.156 IMEI: 86816500xxxxxxxxx +GCAP: +CGSM,+DS,+ES OK
In my mac the terminal that I need to use is /dev/cu.HUAWEIMobile-Pcui and in Linux is /dev/ttyUSB0.