# ssh_config

This is a Go parser for `ssh_config` files. Importantly, this parser attempts
to preserve comments in a given file, so you can manipulate a `ssh_config` file
from a program, if your heart desires.

It's designed to be used with the excellent
[x/crypto/ssh](https://golang.org/x/crypto/ssh) package, which handles SSH
negotiation but isn't very easy to configure.

The `ssh_config` `Get()` and `GetStrict()` functions will attempt to read values
from `$HOME/.ssh/config` and fall back to `/etc/ssh/ssh_config`. The first
argument is the host name to match on, and the second argument is the key you
want to retrieve.

```go
port := ssh_config.Get("myhost", "Port")
```

Certain directives can occur multiple times for a host (such as `IdentityFile`),
so you should use the `GetAll` or `GetAllStrict` directive to retrieve those
instead.

```go
files := ssh_config.GetAll("myhost", "IdentityFile")
```

You can also load a config file and read values from it.

```go
var config = `
Host *.test
  Compression yes
`

cfg, err := ssh_config.Decode(strings.NewReader(config))
fmt.Println(cfg.Get("example.test", "Port"))
```

Some SSH arguments have default values - for example, the default value for
`KeyboardAuthentication` is `"yes"`. If you call Get(), and no value for the
given Host/keyword pair exists in the config, we'll return a default for the
keyword if one exists.

### Manipulating SSH config files

Here's how you can manipulate an SSH config file, and then write it back to
disk.

```go
f, _ := os.Open(filepath.Join(os.Getenv("HOME"), ".ssh", "config"))
cfg, _ := ssh_config.Decode(f)
for _, host := range cfg.Hosts {
    fmt.Println("patterns:", host.Patterns)
    for _, node := range host.Nodes {
        // Manipulate the nodes as you see fit, or use a type switch to
        // distinguish between Empty, KV, and Include nodes.
        fmt.Println(node.String())
    }
}

// Print the config to stdout:
fmt.Println(cfg.String())
```

## Spec compliance

Wherever possible we try to implement the specification as documented in
the `ssh_config` manpage. Unimplemented features should be present in the
[issues][issues] list.

Notably, the `Match` directive is currently unsupported.

[issues]: https://github.com/kevinburke/ssh_config/issues

## Errata

This is the second [comment-preserving configuration parser][blog] I've written, after
[an /etc/hosts parser][hostsfile]. Eventually, I will write one for every Linux
file format.

[blog]: https://kev.inburke.com/kevin/more-comment-preserving-configuration-parsers/
[hostsfile]: https://github.com/kevinburke/hostsfile

## Donating

I don't get paid to maintain this project. Donations free up time to make
improvements to the library, and respond to bug reports. You can send donations
via Paypal's "Send Money" feature to kev@inburke.com. Donations are not tax
deductible in the USA.

You can also reach out about a consulting engagement: https://burke.services