[PATCH] Fix battery information on FreeBSD

[Ahmed Khanzada]

I just emailed my signed document to become a GNU contributor. I am in
the US so my turnaround should be quick.

Battery status was not working for me on FreeBSD. I have made an
attempt to fix that.

Sorry if I am doing anything wrong. I will need some guidance on this
patching process. I hope to be an efficient GNU contributor soon.

I have only tested this on FreeBSD, as I do not have a laptop with
OpenBSD or NetBSD on it. I was wondering if maybe I should test these
changes on those OSs on some USB stick.

Man documents for APM on each BSD platform:

NetBSD: http://netbsd.gw.com/cgi-bin/man-cgi?apm++NetBSD-current
OpenBSD: https://man.openbsd.org/apm.8
FreeBSD: https://www.freebsd.org/cgi/man.cgi?apm

diff --git a/lisp/battery.el b/lisp/battery.el
index efd2a2181a..b14a9e45c2 100644
--- a/lisp/battery.el
+++ b/lisp/battery.el
@@ -618,30 +618,37 @@ battery-bsd-apm
 %t Remaining battery charge time in the form `h:min'"
   (let* ((os-name (car (split-string
             (shell-command-to-string "/usr/bin/uname"))))
-     (apm-flag (if (equal os-name "OpenBSD") "P" "s"))
-     (apm-cmd (concat "/usr/sbin/apm -ablm" apm-flag))
+     (apm-flag (if (equal os-name "OpenBSD") "Pm"))
+     (apm-flag (if (equal os-name "NetBSD") "sm"))
+     (apm-flag (if (equal os-name "FreeBSD") "st"))
+     (apm-cmd (concat "/usr/sbin/apm -abl" apm-flag))
      (apm-output (split-string (shell-command-to-string apm-cmd)))
+     (battery-status-index (if (equal os-name "FreeBSD") 1 0))
+     (apm-mode-index (if (equal os-name "FreeBSD") 3 4))
+     (battery-percentage-index (if (equal os-name "FreeBSD") 2 1))
+     (battery-life-index (if (equal os-name "FreeBSD") 4 3))
+     (ac-index (if (equal os-name "FreeBSD") 0 3))
      ;; Battery status
      (battery-status
-      (let ((stat (string-to-number (nth 0 apm-output))))
+      (let ((stat (string-to-number (nth battery-status-index apm-output))))
         (cond ((eq stat 0) '("high" . ""))
           ((eq stat 1) '("low" . "-"))
           ((eq stat 2) '("critical" . "!"))
           ((eq stat 3) '("charging" . "+"))
           ((eq stat 4) '("absent" . nil)))))
      ;; Battery percentage
-     (battery-percentage (nth 1 apm-output))
+     (battery-percentage (nth battery-percentage-index apm-output))
      ;; Battery life
-     (battery-life (nth 2 apm-output))
+     (battery-life (nth battery-life-index apm-output))
      ;; AC status
      (line-status
-      (let ((ac (string-to-number (nth 3 apm-output))))
+      (let ((ac (string-to-number (nth ac-index apm-output))))
         (cond ((eq ac 0) "disconnected")
           ((eq ac 1) "connected")
           ((eq ac 2) "backup power"))))
      ;; Advanced power savings mode
      (apm-mode
-      (let ((apm (string-to-number (nth 4 apm-output))))
+      (let ((apm (string-to-number (nth apm-mode-index apm-output))))
         (if (string= os-name "OpenBSD")
         (cond ((eq apm 0) "manual")
               ((eq apm 1) "automatic")