android bash linux shell

grep command not found in adb shell

After my phone is connected to the computer through adb, going to adb shell and then typing grep gives me

grep: not found  

Is this a problem with my adb installation or my phone? How do I get grep to work for my device?

PS: This is the reason why I think it might a problem with my phone (as opposed to the adb installation)

The answer says

The grep utility may not be installed on your device.

However, I may have misunderstood the statement. How do I get grep working?