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### 4.11 Selecting config files for user/host name completion

The variable `tramp-completion-function-alist` is intended to customize which files are taken into account for user and host name completion (see Filename completion). For every method, it keeps a set of configuration files, accompanied by a Lisp function able to parse that file. Entries in `tramp-completion-function-alist` have the form (method pair1 pair2 ...).

Each pair is composed of (function file). function is responsible to extract user names and host names from file for completion. There are two functions which access this variable:

— Function: tramp-get-completion-function method

> This function returns the list of completion functions for method.

> Example:

>               (tramp-get-completion-function "rsh")

>                    ⇒ ((tramp-parse-rhosts "/etc/hosts.equiv")
>                        (tramp-parse-rhosts "~/.rhosts"))

— Function: tramp-set-completion-function method function-list

> This function sets function-list as list of completion functions for method.

> Example:

>               (tramp-set-completion-function "ssh"
>                '((tramp-parse-sconfig "/etc/ssh_config")
>                  (tramp-parse-sconfig "~/.ssh/config")))

>                    ⇒ ((tramp-parse-sconfig "/etc/ssh_config")
>                        (tramp-parse-sconfig "~/.ssh/config"))

The following predefined functions parsing configuration files exist:

`tramp-parse-rhosts`
  This function parses files which are syntactical equivalent to `~/.rhosts`. It returns both host names and user names, if specified.
`tramp-parse-shosts`
  This function parses files which are syntactical equivalent to `~/.ssh/known_hosts`. Since there are no user names specified in such files, it can return host names only.
`tramp-parse-sconfig`
  This function returns the host nicknames defined by `Host` entries in `~/.ssh/config` style files.
`tramp-parse-shostkeys`
  SSH2 parsing of directories `/etc/ssh2/hostkeys/*` and `~/ssh2/hostkeys/*`. Hosts are coded in file names `hostkey_portnumber_host-name.pub`. User names are always `nil`.
`tramp-parse-sknownhosts`
  Another SSH2 style parsing of directories like `/etc/ssh2/knownhosts/*` and `~/ssh2/knownhosts/*`. This case, hosts names are coded in file names `host-name.algorithm.pub`. User names are always `nil`.
`tramp-parse-hosts`
  A function dedicated to `/etc/hosts` style files. It returns host names only.
`tramp-parse-passwd`
  A function which parses `/etc/passwd` like files. Obviously, it can return user names only.
`tramp-parse-netrc`
  Finally, a function which parses `~/.netrc` like files.

If you want to keep your own data in a file, with your own structure, you might provide such a function as well. This function must meet the following conventions:

— Function: my-tramp-parse file

> file must be either a file name on your host, or `nil`. The function must return a list of (user host), which are taken as candidates for user and host name completion.

> Example:

>               (my-tramp-parse "~/.my-tramp-hosts")

>                    ⇒ ((nil "toto") ("daniel" "melancholia"))