Provide a function to easily return Hosts

[Dentrax]

Currently we have to manually decode the configuration file:

f, _ := os.Open(filepath.Join(os.Getenv("HOME"), ".ssh", "config"))
cfg, _ := ssh_config.Decode(f)
// cfg.Hosts

It'd be nice to have a function like ssh_config.GetHosts(). It should defaults to DefaultUserSettings unless overridden the config path from the parameters.

[kke]

The ssh_config does not define a list of "hosts" but a list of host matchers, global options, includes and match blocks. There's no point in getting a "list of hosts".

You can have something like:

Host *.example.com
  Port 31

Host secure.example.com
  StrictHostKeyChecking yes

Host !secure.example.com,*.example.com
  IdentityFile ~/foo

This will apply Port and StrictHostKeyChecking when connecting to secure.example.com and Port and IdentityFile when connecting to something-else.example.com.

[firelizzard18]

There is definitely a point: if for no other reason, I want tab-completion for my shell command, like what is available for the ssh command.

[kke]

There is definitely a point: if for no other reason, I want tab-completion for my shell command, like what is available for the ssh command.

I checked how the ssh completion works:

If you have already entered ssh -F <configname> it uses <configname> as the config filename, otherwise it uses the default locations (/etc/ssh/known_hosts and ~/.ssh/known_hosts and a couple of deprecated ones). It doesn't seem to follow any Include directives inside the configs.

It then scans the config(s) and looks for known_hosts file paths in GlobalKnownHostsFile and UserKnownHostsFile directives or falls back to default locations and then parses hostnames from the known hosts files.

It also looks for files in the ssh directories called key_22_<hostname>.pub and uses the <hostname> part.

Then, if it was invoked with the -a param (seems to be by default at least on mac) it uses sed on the ssh configs to find lines matching HostName or Host with params that do not contain wildcard patterns. (I spotted a bug here, it doesn't exclude lines that contain !negated.matchers for Host.) It doesn't look at the HostKeyAlias fields (perhaps intentionally, perhaps an omission?)

Then it tries to complete the hostnames using avahi-browses completion mechanism.

Finally it falls back to the completion system's internal hostname function (which looks at /etc/hosts).

It doesn't use anything but sed to "parse" the ssh configs, the ssh binary is only used for completing things like cipher names.

So, parsing the ssh config is just a small part of the ssh command's hostname completion and even that doesn't do it properly (doesn't follow Includes). If you want to duplicate that, you're better off using the same function in your completion, it's part of the bash_completion package itself, so if the user has bash completion, they also have the _known_hosts_real function available for use.

I didn't look into how it's done for other shells, but quite often it's done by leveraging the existing bash completion scripts.

[firelizzard18]

Or I could add a ForEach(func(*Host)) method, tweak Pattern to track if the pattern has meta characters, and use that to return a list of matching hosts. Which I did. And it was a lot easier than screwing around with someone else's shell functions.