From 61bf53f5d035303b5f6f6f6a0c649529e3dfbdd0 Mon Sep 17 00:00:00 2001
From: Ivan Vilata-i-Balaguer <ivan@selidor.net>
Date: Mon, 19 Sep 2016 11:11:05 +0200
Subject: [PATCH] Fix Debian-specific checking for dmenu.

The old check uses ``which``, which is a Debian-specific tool.  The new one
invokes ``dmenu -v`` straight away, so it doesn't depend on external tools.
It's compatible with both Python 3 and Python 2.

It also fixes opening ``/dev/null`` in write mode instead of read-only, plus
it uses ``with`` to ensure that the file is closed.
---
 quickswitch.py | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/quickswitch.py b/quickswitch.py
index ca9b45f..925225a 100755
--- a/quickswitch.py
+++ b/quickswitch.py
@@ -37,11 +37,14 @@
 
 def check_dmenu():
     '''Check if dmenu is available.'''
-    devnull = open(os.devnull)
-    retcode = subprocess.call(["which", "dmenu"],
-                              stdout=devnull,
-                              stderr=devnull)
-    return True if retcode == 0 else False
+    with open(os.devnull, 'w') as devnull:
+        try:
+            retcode = subprocess.call(["dmenu", "-v"],
+                                      stdout=devnull,
+                                      stderr=devnull)
+            return retcode == 0
+        except OSError:
+            return False
 
 
 def dmenu(options, dmenu):