add 'which' function to utils and use for 'iwgetid'

bumblebee/util.py

@@ -60,4 +60,21 @@ def durationfmt(duration, shorten=False, suffix=False):
 
     return "{}{}".format(res, suf if suffix else "")
 
+def which(program):
+    import os
+    def is_exe(fpath):
+        return os.path.isfile(fpath) and os.access(fpath, os.X_OK)
+
+    fpath, fname = os.path.split(program)
+    if fpath:
+        if is_exe(program):
+            return program
+    else:
+        for path in os.environ["PATH"].split(os.pathsep) + ["/sbin", "/usr/sbin/", "/usr/local/sbin"]:
+            exe_file = os.path.join(path, program)
+            if is_exe(exe_file):
+                return exe_file
+
+    return None
+
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