Possible Duplicate:
Hard link not works under Mac OS X in GUI mode
I did a little experiment. First I ran the following in a Terminal:
mkdir test
cd test
echo "A" > a
echo "B" > b
ln a.txt c
Now a and c have the same content, A, and the same inode number. I can then edit c, using vim, to contain C instead of A and a will also contain C, since they are the same file.
However, if I do the same experiment again but use TextEdit instead of vim it seems to create a new file when I save it. c gets a new inode number and a still contains A. Why is this? What's going on?