diff --git a/Lib/pipes.py b/Lib/pipes.py
index 6a473ae..51666a8 100644
--- a/Lib/pipes.py
+++ b/Lib/pipes.py
@@ -249,20 +249,18 @@
 
 # Reliably quote a string as a single argument for /bin/sh
 
-_safechars = string.ascii_letters + string.digits + '!@%_-+=:,./' # Safe unquoted
-_funnychars = '"`$\\'                           # Unsafe inside "double quotes"
+# Safe unquoted
+_safechars = frozenset(string.ascii_letters + string.digits + '@%_-+=:,./')
 
 def quote(file):
+    """Return a shell-escaped version of the file string."""
     for c in file:
         if c not in _safechars:
             break
     else:
+        if not file:
+            return "''"
         return file
-    if '\'' not in file:
-        return '\'' + file + '\''
-    res = ''
-    for c in file:
-        if c in _funnychars:
-            c = '\\' + c
-        res = res + c
-    return '"' + res + '"'
+    # use single quotes, and put single quotes into double quotes
+    # the string $'b is then quoted as '$'"'"'b'
+    return "'" + file.replace("'", "'\"'\"'") + "'"