Bring back cd context manager

This has been in pyi2ncommon before but was removed since it was only used
in one place (which exists no more). Now needed it again, so bring it back.

diff --git a/src/sysmisc.py b/src/sysmisc.py
index d7fe611..6898f31 100644 (file)
--- a/src/sysmisc.py
+++ b/src/sysmisc.py
@@ -73,6 +73,9 @@ cheat_reboot
 cmd_block_till
     Run a command and wait until a condition evaluates to True.
 
+cd
+    A context manager that temporarily changes the current working directory
+
 The logging functions either use the format capability or play
 the simple role of providing shorter names.
 
@@ -92,6 +95,7 @@ import stat
 import time
 import types
 import uuid
+from contextlib import contextmanager
 import logging
 llog = logging.getLogger('pyi2ncommon.sysmisc')
 
@@ -103,6 +107,26 @@ __all__ = ("inf", "run_cmd_with_pipe", "get_mountpoints_by_type", "read_linewise
 # HELPERS
 ###############################################################################
 
+@contextmanager
+def cd(path):
+    """
+    A context manager which changes the working directory.
+
+    Changes current working directory to the given path, and then changes it
+    back to its previous value on exit.
+
+    Taken from comment for python recipe by Greg Warner at
+    http://code.activestate.com/recipes/576620-changedirectory-context-manager/
+    (MIT license)
+    """
+    orig_wd = os.getcwd()
+    os.chdir(path)
+    try:
+        yield
+    finally:
+        os.chdir(orig_wd)
+
+
 def run_cmd_with_pipe(argv, inp=None):
     """
     Read from a process pipe.