;; Set the modeline to tell me the filename, hostname, etc..
(setq-default mode-line-format
  (list " "
        ; */% indicators if the file has been modified
        'mode-line-modified
        "--"
        ; the name of the buffer (i.e. filename)
        ; note this gets automatically highlighted
        'mode-line-buffer-identification
        "--"
        ; major and minor modes in effect
        'mode-line-modes
        ; if which-func-mode is in effect, display which
        ; function we are currently in.
        '(which-func-mode ("" which-func-format "--"))
        ; line, column, file %
        'mode-line-position
        "--"
        ; if vc-mode is in effect, display version control
        ; info here
        `(vc-mode vc-mode)
        "--"
        ; hostname
        'system-name
        ; dashes sufficient to fill rest of modeline.
        "-%-"
        )
)

(let ((pos (memq 'mode-line-modes mode-line-format)))
  (setcdr pos (cons (getenv "HOSTNAME") (cdr pos))))

(setq-default mode-line-format (build-list-that-contains-(getenv "HOSTNAME")))