/home/ricmoo> ethers --account mnemonic.txt --xxx-mnemonic-password
Password (mnemonic; experimental - hard): ******
Decrypting... 100%
network: homestead (chainId: 1)
homestead> accounts[0].getAddress()
<Promise id=0 resolved>
'0x56FC8792cC17971C19bEC4Ced978beEA44711EeD'
homestead>