02/02: doc: Add an example to the documentation of the udev-service.

[Ricardo Wurmus]

rekado pushed a commit to branch master
in repository guix.

commit e0c1d080b520c1bbd2dcd7bc90a750f5ce580486
Author: Ricardo Wurmus <address@hidden>
Date:   Mon Oct 9 23:03:56 2017 +0200

    doc: Add an example to the documentation of the udev-service.
    
    * doc/guix.texi (Base Services): Update 'udev-service' documentation.
---
 doc/guix.texi | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 6018198..b7f4f88 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -9790,8 +9790,32 @@ Return a service that runs the Guix build daemon 
according to
 @var{config}.
 @end deffn
 
address@hidden {Scheme Procedure} udev-service [#:udev udev]
address@hidden udev-service
address@hidden udev-rule
address@hidden {Scheme Procedure} udev-service [#:udev @var{udev}] [#:rules 
@var{'()}]
 Run @var{udev}, which populates the @file{/dev} directory dynamically.
+Additional udev rules can be provided as a list of files through the
address@hidden variable.  The procedure @var{udev-rule} simplifies the
+creation of these rule files.
+
+In the following example, a rule for a USB device is defined to be
+stored in the file @file{90-usb-thing.rules}, and the default
address@hidden is extended with it.  The rule runs a script upon
+detecting a USB device with a given product identifier.
+
address@hidden
+(define %example-udev-rule
+  (udev-rule "90-usb-thing.rules"
+             "ACTION==\"add\", SUBSYSTEM==\"usb\", 
address@hidden@}==\"Example\", RUN+=\"/path/to/script\""))
+
+(operating-system
+  ;; @dots{}
+  (services (modify-services %desktop-services
+              (udev-service-type config =>
+                (udev-configuration (inherit config)
+                  (rules (append (udev-configuration-rules config)
+                                 (list %example-udev-rule))))))))
address@hidden example
 @end deffn
 
 @deffn {Scheme Procedure} urandom-seed-service @var{#f}