You may read my guide about Sendmodem program to send AT commands to your iPhone baseband. You can use these commands to get some baseband information for unlock or other thinks. Also you can read about Minicom. You can use this link to go there. But today I want to introduce you another program for this which is called iGSM. The new iGSM tool was developed to send AT commands. This tool was created by Marcio’s iPhone Apps and uses /dev/tty.debug without need to disable the commcenter during the process and has function to perform these jobs which means that you don’t need to manually enter: 
launchctl unload -w /System/Library/LaunchDaemons/com.apple.CommCenter.plist
which will unload CommCenter process from iPhone Baseband RAM.

iGSM Tool

You may hear about Sendmodem tool which has the same possibilities as iGSM and if you would like to use Sendmodem then go here for instruction. But I must tell you that iGSM tool is more powerful then Sendmodem, however they are the same in general.

Download iGSM

You can download iGSM tool using this command: 
wget /scripts/igsm.zip
unzip igsm.zip
Usually, the iPhone baseband is accessed via minicom which add commands to /dev/tty.baseband. To make sure that minicom functions, the commcenter first must be disabled, after that your can run minicom, and after you are completed with minicom you again have to enable the CommCenter.plist file.

How to run iGSM

Open terminal and navigate to the directory where you have downloaded the igsm file. Then perform this command: 
sudo +x igsm
Now you are ready to run the tool. You can see that igsm tool is more convenient. So let's begin but first look at the meanings of the shortens that you need to issue using this script: 
igsm [-p pin] [-c command ... -c command] [-l] [-L] [-u] [-d] [-v] [-r]
-p pin SIM pin (if needed)
-d dump IMEI IMSI …
-c cmd command to be executed (more than 1 is supported)
-l load commcenter
-L list all jobs loaded into launchd
-u unload commcenter
-r reset baseband
-m string modem init string
-M num max lines on any command
-v verbose mode
-vv verbose mode and hex dump
-h this help
-hh extended help
Also with igsm commands to iPhone baseband (modem) can be directly carried out from the commandline. Here below you can see my example of usage igsm tool to get the baseband info for your needs.

Example of usage iGSM to get the baseband info

igsm -c AT+CPBS?
 Opened: /dev/tty.baseband
 > ATE0 – set echo OFF
 < OK
> AT
 < OK
> AT+CPIN? – SIM requires PIN ?
 < +CPIN: READY
 < OK
> AT+CPBS?
 < +CPBS: “SM”,34,150
 < OK
 Done
And that's it now you have entered your baseband and can see all its info that can be needing for making unlock or see bootloader version or something that can be needed by you from your iPhone baseband. Also you can see this list soon of AT commands to use it for your needs.