Why is my script not going up one level when using /../? - bash

Question

I have the understanding that using "/../" in a file location in bash will go up one level. That's what I'm trying to do here:
for box in {0..4}
do
for lvl in {0..24}
do
key="UNLOCKED_${box}_$lvl"
plutil -key "$key" -value '1' "$appdir/../Library/Preferences/com.chillingo.cuttherope.plist" 2>&1> /dev/null
#successCheck=$(plutil -key "$key" "/$appdir/../Library/Preferences/com.chillingo.cuttherope.plist")
#if [ "$successCheck" -lt 1 ]; then
# echo "Level ${box}-$lvl failed! "
#fi
done
done
But I keep getting this error (x125):
Error: File not found at path /var/mobile/Applications/1E17CC78-AA6E-4FFA-B241-74A73FE3AB0E/CutTheRope.app/../Library/Preferences/com.chillingo.cuttherope.plist
Any help would be greatly appreciated/
Thanks.

Answer 1

/ means start from the root of the filesystem or context, and ../ means go up one level. /../ effectively cancels the two out.
To go up one level, try ../
EDIT: In other words, try removing the / from the end of the variable in your path.
EDIT #2: The best solution is to probably just remove the /../
EDIT #3:
This would work:
/var/mobile/Applications/1E17CC78-AA6E-4FFA-B241-74A73FE3AB0E/CutTheRope.app/Library/../Library/Preferences/
And if you removed the second Library and the .. it should also work:
/var/mobile/Applications/1E17CC78-AA6E-4FFA-B241-74A73FE3AB0E/CutTheRope.app/Library/Preferences/

Answer 2

The lookup procedure is as follows:
inode lookup(string path) {
inode cur = path[0] == '/' ? process->root_directory : process->current_directory;
foreach component in split(path, '/') {
inode next = cur.get_entry(component);
if (next is a file && the component is the last one)
return;
if (next is a directory)
cur = next;
else
return null;
}
return cur;
}
There is no special handling for ... The point is that a file can only appear as the very last component of the path. If it appears before, the return null path will be taken.
The actual implementation (for example in NetBSD) is a bit more complicated.
Update: I just saw that in your question $appdir will probably point to a directory, so the above discussion does not apply. Still, there might be some symlinks involved. When you follow a symlink and then continue with .., the lookup function continues from where the symlink points to. A small example:
$ ln -s somewhere/else/deep/in/the/path symlink
$ ls -l symlink/..
This will resolve to somewhere/else/deep/in/the (provided it exists). The lookup function will not simplify the path symlink/.. to . or as another example first/../second will not be simplified to second.