Possible bug in readlink, canonicalize fails.

[mpb]

Hi,

I believe the following script demonstrates that readlink cannot
always canonicalize paths.  It may be possible to create a simpler
demonstration of the bug, but I could not trivially do so.

Thanks!

-mpb

----------------------------------

#! /bin/bash


# Clean up previous demonstations of the bug.
if [ -a /tmp/a0 ]; then  rm -r /tmp/a0;  fi
if [ -a /tmp/c0 ]; then  rm -r /tmp/c0;  fi


# Create 3 directories.
mkdir -p /tmp/a0/a1/a2/a3/a4/a5
mkdir -p /tmp/a0/a1/a2/b3/b4
mkdir -p /tmp/c0


# Create 1 file.
echo 'I am a6.' > /tmp/a0/a1/a2/a3/a4/a5/a6


# Create 3 symbolic links inside those directories.
ln -s a1/a2         /tmp/a0/a2
ln -s /tmp/a0/a2/b3 /tmp/c0/b3
ln -s /tmp/a0/a2/a3/a4/a5 /tmp/c0/b3/b4/a5


# Show what we have created.
find /tmp/a0 /tmp/c0


# Specify a convoluted (but valid) path to the file a6.
path=/tmp/c0/b3/b4/a5/a6


# Look!  The file exists at $path!
echo
echo The file exists ...
ls -l $path
cat   $path


# But readlink cannot canonicalize it!
echo
echo ... but readlink cannot canonicalize it!
readlink -f $path
echo "readlink exit status: $?"
readlink -e $path
echo "readlink exit status: $?"
readlink -m $path
echo "readlink exit status: $?"


# I am running: "readlink (GNU coreutils) 6.9"
echo
readlink --version

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When I run the script, I get the following output:

$ bash bug.sh
/tmp/a0
/tmp/a0/a1
/tmp/a0/a1/a2
/tmp/a0/a1/a2/a3
/tmp/a0/a1/a2/a3/a4
/tmp/a0/a1/a2/a3/a4/a5
/tmp/a0/a1/a2/a3/a4/a5/a6
/tmp/a0/a1/a2/b3
/tmp/a0/a1/a2/b3/b4
/tmp/a0/a1/a2/b3/b4/a5
/tmp/a0/a2
/tmp/c0
/tmp/c0/b3

The file exists ...
-rw-r--r-- 1 asterisk asterisk 9 Sep 21 00:39 /tmp/c0/b3/b4/a5/a6
I am a6.

... but readlink cannot canonicalize it!
readlink exit status: 1
readlink exit status: 1
/tmp/a0/a2/a3/a4/a5/a6
readlink exit status: 0

readlink (GNU coreutils) 6.9
Copyright (C) 2007 Free Software Foundation, Inc.
This is free software.  You may redistribute copies of it under the terms of
the GNU General Public License <http://www.gnu.org/licenses/gpl.html>.
There is NO WARRANTY, to the extent permitted by law.

Written by Dmitry V. Levin.