To connect to a running Asterisk session:
asterisk -rvvv

To issue a command to Asterisk from the shell:
asterisk -rx "<command>"

To originate an echo call from a SIP trunk on an Asterisk server, to a specified number:
asterisk -rx "channel originate SIP/<trunk>/<number> application echo"

To print out the details of SIP accounts:
asterisk -rx "sip show peers"

To print out the passwords of SIP accounts:
asterisk -rx "sip show users"

To print out the current active channels:
asterisk -rx "core show channels"