[file_utils] unln: handle exceptions, list errors

file_utils/README

@@ -25,6 +25,11 @@ equivalent of (cp -p file tmp && mv tmp file). Checks are done in order
 to work only on regular files which have more than one hard link, so the
 minimal amount of copies are done.
 
+A summary of the file names on which error were raised is displayed at
+the end of the execution. Note that if a file is under a directory which
+is not executable (i.e. the program can't cd in), it will be considered
+as inexistant and ignored, and its name won't be displayed.
+
 /!\ Warning: the copy function used is shutil.copy2(), which tries to
     preserve all the metadata it can, but as of Python 3.3 it is not
     guaranteed that extended attributes will be preserved. See the

file_utils/unln.py

@@ -29,10 +29,8 @@
 # inodes by doing the equivalent of (cp -p file tmp && mv tmp file).
 #
 # TODO:
-# - Handle exceptions (permission denied on copy, etc.)
 # - Option verbose
 # - Option to follow symlinks
-# - Summarise skipped regular files with more than one link
 
 
 import sys
@@ -90,6 +88,10 @@ usage_string = "Usage:\n\t{} <file1> [file2 ...]".format(progname)
 # Error codes
 ERR_BAD_USAGE = 1
 
+# List of filenames that were supposed to be worked on but could not because of
+# an error
+error_filenames = []
+
 
 # Check command-line arguments
 if len(sys.argv) < 2:
@@ -123,17 +125,31 @@ for filename in sys.argv[1:]:
 
     # Reserve a temporary file name
     dirname = os.path.dirname(filename)
-    handle, tmpfilename = tempfile.mkstemp(
-        prefix="{}-".format(filename),
-        suffix="-{}.tmp".format(progname),
-        dir=dirname)
+    try:
+        handle, tmpfilename = tempfile.mkstemp(
+            prefix="{}-".format(filename),
+            suffix="-{}.tmp".format(progname),
+            dir=dirname)
+    except:
+        warn("Cannot create temporary file to copy {}:".format(quote(filename)),
+             sys.exc_info()[1])
+        error_filenames.append(filename)
+        continue
     os.close(handle) # we just need a temporary file name
 
     # Copy the original file to the temporary file
     verbose("Copying to temporary file", quote(tmpfilename), end="... ")
-    shutil.copy2(filename, tmpfilename) # cp -p
+    try:
+        shutil.copy2(filename, tmpfilename) # cp -p
+    except:
+        warn("Cannot copy {} to {}:".format(quote(filename), quote(tmpfilename)),
+             sys.exc_info()[1])
+        error_filenames.append(filename)
+        # Delete temporary file
+        os.remove(tmpfilename)
+        continue
 
-    # Try to sync if we are running Python >= 3.3
+    # Sync (if we are running Python >= 3.3)
     if sys.version_info.minor >= 3:
         verbose("Syncing", end="... ")
         os.sync()
@@ -141,4 +157,18 @@ for filename in sys.argv[1:]:
     # Rename the temporary file with the original file name
     verbose("Moving back {} to {}...".format(
             quote(tmpfilename), quote(filename)))
-    os.rename(tmpfilename, filename)
+    try:
+        os.rename(tmpfilename, filename)
+    except:
+        warn("Cannot move {} to {}:".format(
+                quote(tmpfilename), quote(filename)),
+             sys.exc_info()[1], "Deleting temporary file", quote(tmpfilename))
+        error_filenames.append(filename)
+        # Delete temporary file
+        os.remove(tmpfilename)
+
+
+# Display the list of files in error
+if len(error_filenames):
+    warn("The following regular files still have more than one hard link:")
+    print(*error_filenames, sep="\n", file=sys.stderr)