nixos/acpid: pass event parameters to handler (#34190)

Previously the parameters were just dropped. Now they can be read
from within the handler script. An example to show this is added.

Makes use of the new writeShellScript function as suggested in:
issue #21557

resolves:  #21557

1 files changed, 27 insertions, 5 deletions

diff --git a/nixos/modules/services/hardware/acpid.nix b/nixos/modules/services/hardware/acpid.nix
index bb17c8859d8..f69706ebff3 100644
--- a/nixos/modules/services/hardware/acpid.nix
+++ b/nixos/modules/services/hardware/acpid.nix
@@ -31,7 +31,7 @@ let
           ''
             fn=$out/${name}
             echo "event=${handler.event}" > $fn
-            echo "action=${pkgs.writeScript "${name}.sh" (concatStringsSep "\n" [ "#! ${pkgs.bash}/bin/sh" handler.action ])}" >> $fn
+            echo "action=${pkgs.writeShellScriptBin "${name}.sh" handler.action }/bin/${name}.sh '%e'" >> $fn
           '';
         in concatStringsSep "\n" (mapAttrsToList f (canonicalHandlers // config.services.acpid.handlers))
       }
@@ -69,11 +69,33 @@ in
           };
         });
 
-        description = "Event handlers.";
-        default = {};
-        example = { mute = { event = "button/mute.*"; action = "amixer set Master toggle"; }; };
-
+        description = ''
+          Event handlers.
 
+          <note><para>
+            Handler can be a single command.
+          </para></note>
+        '';
+        default = {};
+        example = {
+          ac-power = {
+            event = "ac_adapter/*";
+            action = ''
+              vals=($1)  # space separated string to array of multiple values
+              case ''${vals[3]} in
+                  00000000)
+                      echo unplugged >> /tmp/acpi.log
+                      ;;
+                  00000001)
+                      echo plugged in >> /tmp/acpi.log
+                      ;;
+                  *)
+                      echo unknown >> /tmp/acpi.log
+                      ;;
+              esac
+            '';
+          };
+        };
       };
 
       powerEventCommands = mkOption {