fish-shell/share/functions/__fish_print_hostnames.fish

function __fish_print_hostnames -d "Print a list of known hostnames"
    # HACK: This only deals with ipv4

    # Print all hosts from /etc/hosts
    # use 'getent hosts' on OSes that support it (OpenBSD and Cygwin do not)
    if type -q getent
        and getent hosts >/dev/null 2>&1 # test if 'getent hosts' works and redirect output so errors don't print
        # Ignore zero ips
        getent hosts | string match -r -v '^0.0.0.0' | string replace -r '[0-9.]*\s*' '' | string split " "
    else if test -r /etc/hosts
        # Ignore commented lines and functionally empty lines
        string match -r -v '^\s*0.0.0.0|^\s*#|^\s*$' </etc/hosts # Strip comments
| string replace -ra '#.*$' '' | string replace -r '[0-9.]*\s*' '' | string trim | string replace -ra '\s+' '\n'
end

# Print nfs servers from /etc/fstab
if test -r /etc/fstab
    string match -r '^\s*[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3]:|^[a-zA-Z\.]*:' </etc/fstab | string replace -r ':.*' ''
end

# Check hosts known to ssh
set -l known_hosts ~/.ssh/known_hosts{,2} /etc/ssh/known_hosts{,2} # Yes, seriously - the default specifies both with and without "2"
for file in /etc/ssh/ssh_config ~/.ssh/config
    if test -r $file
        # Print hosts from system wide ssh configuration file
        # Note the non-capturing group to avoid printing "name"
        string match -ri '\s*Host(?:name)?(?:\s+|\s*=\s*)\w.*' <$file | string replace -ri '^\s*Host(?:name)?\s*(\S+)' '$1' | string replace -r '\s+' ' ' | string split ' '
        set known_hosts $known_hosts (string match -ri '^\s*UserKnownHostsFile|^\s*GlobalKnownHostsFile' < $file \
				| string replace -ri '.*KnownHostsFile\s*' '')
    end
end
for file in $known_hosts
    # Ignore hosts that are hashed, commented or have custom ports (like [localhost]:2200)
    test -r $file
    and string replace -ra '(\S+) .*' '$1' <$file | string match -r '^[^#|[=]+$' | string split ","
end
return 0
end