add path.get_ipython_cache_dir to retrieve a cache directory

IPython/utils/path.py

@@ -244,6 +244,24 b' def get_xdg_dir():'
     return None
 
 
+def get_xdg_cache_dir():
+    """Return the XDG_CACHE_HOME, if it is defined and exists, else None.
+
+    This is only for non-OS X posix (Linux,Unix,etc.) systems.
+    """
+
+    env = os.environ
+
+    if os.name == 'posix' and sys.platform != 'darwin':
+        # Linux, Unix, AIX, etc.
+        # use ~/.cache if empty OR not set
+        xdg = env.get("XDG_CACHE_HOME", None) or os.path.join(get_home_dir(), '.cache')
+        if xdg and _writable_dir(xdg):
+            return py3compat.cast_unicode(xdg, fs_encoding)
+
+    return None
+
+
 def get_ipython_dir():
     """Get the IPython directory for this platform and user.
 
@@ -300,6 +318,20 b' def get_ipython_dir():'
     return py3compat.cast_unicode(ipdir, fs_encoding)
 
 
+def get_ipython_cache_dir():
+    """Get the cache directory it is created if it does not exist."""
+    xdgdir = get_xdg_cache_dir()
+    if xdgdir is None:
+        return get_ipython_dir()
+    ipdir = os.path.join(xdgdir, "ipython")
+    if not os.path.exists(ipdir) and _writable_dir(xdgdir):
+        os.makedirs(ipdir)
+    elif not _writable_dir(xdgdir):
+        return get_ipython_dir()
+
+    return py3compat.cast_unicode(ipdir, fs_encoding)
+
+
 def get_ipython_package_dir():
     """Get the base directory where IPython itself is installed."""
     ipdir = os.path.dirname(IPython.__file__)

IPython/utils/tests/test_path.py

@@ -60,6 +60,7 b' TEST_FILE_PATH = split(abspath(__file__))[0]'
 TMP_TEST_DIR = tempfile.mkdtemp()
 HOME_TEST_DIR = join(TMP_TEST_DIR, "home_test_dir")
 XDG_TEST_DIR = join(HOME_TEST_DIR, "xdg_test_dir")
+XDG_CACHE_DIR = join(HOME_TEST_DIR, "xdg_cache_dir")
 IP_TEST_DIR = join(HOME_TEST_DIR,'.ipython')
 #
 # Setup/teardown functions/decorators
@@ -74,6 +75,7 b' def setup():'
     # problem because that exception is only defined on Windows...
     os.makedirs(IP_TEST_DIR)
     os.makedirs(os.path.join(XDG_TEST_DIR, 'ipython'))
+    os.makedirs(os.path.join(XDG_CACHE_DIR, 'ipython'))
 
 
 def teardown():
@@ -361,6 +363,26 b' def test_filefind():'
     t = path.filefind(f.name, alt_dirs)
     # print 'found:',t
 
+@with_environment
+def test_get_ipython_cache_dir():
+    os.environ["HOME"] = HOME_TEST_DIR
+    if os.name == 'posix' and sys.platform != 'darwin':
+        # test default
+        os.makedirs(os.path.join(HOME_TEST_DIR, ".cache"))
+        os.environ.pop("XDG_CACHE_HOME", None)
+        ipdir = path.get_ipython_cache_dir()
+        nt.assert_equal(os.path.join(HOME_TEST_DIR, ".cache", "ipython"),
+                        ipdir)
+        nt.assert_true(os.path.isdir(ipdir))
+
+        # test env override
+        os.environ["XDG_CACHE_HOME"] = XDG_CACHE_DIR
+        ipdir = path.get_ipython_cache_dir()
+        nt.assert_true(os.path.isdir(ipdir))
+        nt.assert_equal(ipdir, os.path.join(XDG_CACHE_DIR, "ipython"))
+    else:
+        nt.assert_equal(path.get_ipython_cache_dir(),
+                        path.get_ipython_dir())
 
 def test_get_ipython_package_dir():
     ipdir = path.get_ipython_package_dir()