Manage loaded ssh keys in the ssh-agent. Ensure that ssh-agent is up and running for the keys to be loaded in it.

# To add the default ssh keys in "~/.ssh" to the ssh-agent:
ssh-add

# To add a specific key to the ssh-agent:
ssh-add path/to/private_key

# To list fingerprints of currently loaded keys:
ssh-add -l

# To delete a key from the ssh-agent:
ssh-add -d path/to/private_key

# To delete all currently loaded keys from the ssh-agent:
ssh-add -D

# To add a key to the ssh-agent and the keychain:
ssh-add -K path/to/private_key