diff -r 524a032c8e0f Doc/library/os.rst
--- a/Doc/library/os.rst	Tue Feb 21 22:10:16 2012 +0100
+++ b/Doc/library/os.rst	Wed Feb 22 00:46:11 2012 +0100
@@ -1881,6 +1881,16 @@ Files and Directories
       Added support for Windows 6.0 (Vista) symbolic links.
 
 
+.. function:: realpath(path)
+
+   Return a string representing the canonicalized pathname of *path*.
+   See :manpage:`realpath(3)` for more information.
+
+   Availability: Unix
+
+   .. versionadded:: 3.3
+
+
 .. function:: remove(path)
 
    Remove (delete) the file *path*.  If *path* is a directory, :exc:`OSError` is
diff -r 524a032c8e0f Lib/posixpath.py
--- a/Lib/posixpath.py	Tue Feb 21 22:10:16 2012 +0100
+++ b/Lib/posixpath.py	Wed Feb 22 00:46:11 2012 +0100
@@ -380,32 +380,11 @@ def abspath(path):
 
 def realpath(filename):
     """Return the canonical path of the specified filename, eliminating any
-symbolic links encountered in the path."""
-    if isinstance(filename, bytes):
-        sep = b'/'
-        empty = b''
+    symbolic links encountered in the path."""
+    if filename:
+        return os.realpath(filename)
     else:
-        sep = '/'
-        empty = ''
-    if isabs(filename):
-        bits = [sep] + filename.split(sep)[1:]
-    else:
-        bits = [empty] + filename.split(sep)
-
-    for i in range(2, len(bits)+1):
-        component = join(*bits[0:i])
-        # Resolve symbolic links.
-        if islink(component):
-            resolved = _resolve_link(component)
-            if resolved is None:
-                # Infinite loop -- return original component + rest of the path
-                return abspath(join(*([component] + bits[i:])))
-            else:
-                newpath = join(*([resolved] + bits[i:]))
-                return realpath(newpath)
-
-    return abspath(filename)
-
+        return os.getcwd()
 
 def _resolve_link(path):
     """Internal helper function.  Takes a path and follows symlinks
diff -r 524a032c8e0f Modules/posixmodule.c
--- a/Modules/posixmodule.c	Tue Feb 21 22:10:16 2012 +0100
+++ b/Modules/posixmodule.c	Wed Feb 22 00:46:11 2012 +0100
@@ -8167,6 +8167,46 @@ win32__getdiskusage(PyObject *self, PyOb
 #endif
 
 
+#ifdef HAVE_REALPATH
+PyDoc_STRVAR(posix_realpath__doc__,
+"realpath(path) -> path\n\n\
+Return the canonicalized pathname of the given path.");
+
+static PyObject *
+posix_realpath(PyObject *self, PyObject *args)
+{
+    PyObject *opath, *orpath;
+    char *path, *rpath;
+#ifndef HAVE_CANONICALIZE_FILE_NAME
+    char buffer[MAXPATHLEN];
+#endif
+
+    if (!PyArg_ParseTuple(args, "O&:realpath",
+                          PyUnicode_FSConverter, &opath))
+        return NULL;
+    path = PyBytes_AsString(opath);
+
+#ifdef HAVE_CANONICALIZE_FILE_NAME
+    Py_BEGIN_ALLOW_THREADS
+    rpath = canonicalize_file_name(path);
+    Py_END_ALLOW_THREADS
+#else
+    Py_BEGIN_ALLOW_THREADS
+    rpath = realpath(path, buffer);
+    Py_END_ALLOW_THREADS
+#endif
+    if (rpath == NULL)
+        return posix_error_with_allocated_filename(opath);
+    orpath = PyUnicode_DecodeFSDefault(rpath);
+#ifdef HAVE_CANONICALIZE_FILE_NAME
+    free(rpath);
+#endif
+    Py_DECREF(opath);
+    return orpath;
+}
+#endif
+
+
 /* This is used for fpathconf(), pathconf(), confstr() and sysconf().
  * It maps strings representing configuration variable names to
  * integer values, allowing those functions to be called with the
@@ -10927,6 +10967,9 @@ static PyMethodDef posix_methods[] = {
 #ifdef HAVE_PATHCONF
     {"pathconf",        posix_pathconf, METH_VARARGS, posix_pathconf__doc__},
 #endif
+#ifdef HAVE_REALPATH
+    {"realpath",        posix_realpath, METH_VARARGS, posix_realpath__doc__},
+#endif /* HAVE_READLINK */
     {"abort",           posix_abort, METH_NOARGS, posix_abort__doc__},
 #ifdef MS_WINDOWS
     {"_getfullpathname",        posix__getfullpathname, METH_VARARGS, NULL},
diff -r 524a032c8e0f configure
--- a/configure	Tue Feb 21 22:10:16 2012 +0100
+++ b/configure	Wed Feb 22 00:46:11 2012 +0100
@@ -9395,7 +9395,8 @@ fi
 $as_echo "MACHDEP_OBJS" >&6; }
 
 # checks for library functions
-for ac_func in alarm accept4 setitimer getitimer bind_textdomain_codeset chown \
+for ac_func in alarm accept4 setitimer getitimer bind_textdomain_codeset \
+ canonicalize_file_name chown \
  clock confstr ctermid execv faccessat fchmod fchmodat fchown fchownat \
  fexecve fdopendir fork fpathconf fstatat ftime ftruncate futimesat \
  futimens futimes gai_strerror \
@@ -14599,8 +14600,8 @@ esac
 
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 # Files that config.status was made for.
-config_files="`echo $ac_config_files`"
-config_headers="`echo $ac_config_headers`"
+config_files="$ac_config_files"
+config_headers="$ac_config_headers"
 
 _ACEOF
 
diff -r 524a032c8e0f configure.in
--- a/configure.in	Tue Feb 21 22:10:16 2012 +0100
+++ b/configure.in	Wed Feb 22 00:46:11 2012 +0100
@@ -2561,7 +2561,8 @@ fi
 AC_MSG_RESULT(MACHDEP_OBJS)
 
 # checks for library functions
-AC_CHECK_FUNCS(alarm accept4 setitimer getitimer bind_textdomain_codeset chown \
+AC_CHECK_FUNCS(alarm accept4 setitimer getitimer bind_textdomain_codeset \
+ canonicalize_file_name chown \
  clock confstr ctermid execv faccessat fchmod fchmodat fchown fchownat \
  fexecve fdopendir fork fpathconf fstatat ftime ftruncate futimesat \
  futimens futimes gai_strerror \
diff -r 524a032c8e0f pyconfig.h.in
--- a/pyconfig.h.in	Tue Feb 21 22:10:16 2012 +0100
+++ b/pyconfig.h.in	Wed Feb 22 00:46:11 2012 +0100
@@ -101,6 +101,9 @@
 /* Define this if you have the type _Bool. */
 #undef HAVE_C99_BOOL
 
+/* Define to 1 if you have the `canonicalize_file_name' function. */
+#undef HAVE_CANONICALIZE_FILE_NAME
+
 /* Define to 1 if you have the 'chflags' function. */
 #undef HAVE_CHFLAGS