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Re: Writing a Lisp to show the capacity of the battery of the laptop


From: Deniz Dogan
Subject: Re: Writing a Lisp to show the capacity of the battery of the laptop
Date: Tue, 22 Feb 2011 16:33:56 +0100

2011/2/21 Thomas Dean <address@hidden>:
>
> Hi,
>
> I'm using Archlinux. I want to write a lisp to show the remaining
> capacity of the battery of the laptop. It is expected to work like
> this:
>
> 1. Read from /proc/acpi/battery/BAT0/state and obtain the remaining
> capacity of the battery.
> 2. Read from /proc/acpi/battery/BAT0/info and obtain the full capacity
> of the battery.
> 3. By calculating remaining / full, get the percentage and print it.
>
> I writing the following lisp but it seems that it doesn't work.
>
> ;--------------------------------LISP---------------------------------
>
> ; get remaining capacity
> (shell-command
>  "cat /proc/acpi/battery/BAT0/state | grep \"remaining capacity\" | sed 
> \"s/^[a-z][a-z: ]*\([0-9][0-9]*\).*$/\1/g\""
>  "td-battery-temp-buffer")
> (set-buffer "td-battery-temp-buffer")
> (setq td-battery-full (string-to-number (buffer-string)))
> (erase-buffer)
>
> ; get full capacity
> (shell-command
>  "cat /proc/acpi/battery/BAT0/info | grep \"last full capacity\" | sed 
> \"s/^[a-z][a-z: ]*\([0-9][0-9]*\).*$/\1/g\""
>  "td-battery-temp-buffer")
> (setq td-battery-full (string-to-number (buffer-string)))
>
> ; calculate percentage
> (message (concat "Remaining Capacity: " (number-to-string 
> td-battery-remaining)
>                 "\nFull Capacity: " (number-to-string td-battery-full)))
>
> ; kill temporary buffer
> (set-buffer-modified-p nil)
> (kill-buffer)
>
> ;----------------------LISP END-------------------------------
>
> I'm new to lisp :-) So it maybe looks ugly.
>
> Could you please show me a good lisp that can finish this task?
>

Your code is unorganized and buffer-centric for no reason. Below is
some code I wrote, which I can't test at the moment, but it should
give you a few hints. By the way, try M-x battery in Emacs.

(defun bat-remaining ()
  "Return the battery's remaining capacity."
  (let ((result (shell-command "yada yada")))
    (string-to-number result)))

(defun bat-full ()
  "Return the battery's full capacity."
  (let ((result (shell-command "blah blah")))
    (string-to-number result)))

(defun bat-percent ()
  "Return the remaining amount of battery power as an integer."
  (let ((remaining (float (bat-remaining)))
        (full (float (bat-full))))
    (round (* (/ remaining full) 100))))

(defun bat-information ()
  "Echo information about the battery."
  (interactive)
  (message "Remaining capacity: %s\nFull capacity: %s"
           (bat-remaining)
           (bat-full)))


-- 
Deniz Dogan



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