# List all kernel keys (parameters) and their values.
sysctl [--all|-a]
# As above, but show only specified keys and their values.
sysctl [KEY_1 [KEY_2] ...]

# As above, but instead output only the values.
sysctl [--values|-n] [KEY_1 [KEY_2] ...]
# Not nearly as useful, but alternatively, output only the key names.
sysctl [--names|-N] [KEY_1 [KEY_2] ...]

# Assign one or more kernel keys a new value; usually requires root access.
sysctl [KEY_1=VALUE_1 [KEY_2=VALUE_2] ...]