gistfile1.el

(start-process "ls" nil "ls")

(defun keep-output (process output)
  (setq kept (cons output kept)))

(setq kept nil)

(set-process-filter (get-process "ls") 'keep-output)


(set-process-filter (start-process "ls" "foo" "ls") 'keep-output)


(start-process "shell" nil "/bin/bash")

(set-process-filter (get-process "shell") 'keep-output)

(process-send-string "shell" "echo test\n")