diffutils: Special Files
18.1.3 Files that are Neither Directories Nor Regular Files
-----------------------------------------------------------
Some files are neither directories nor regular files: they are unusual
files like symbolic links, device special files, named pipes, and
sockets. Currently, 'diff' treats symbolic links as if they were the
pointed-to files, except that a recursive 'diff' reports an error if it
detects infinite loops of symbolic links (e.g., symbolic links to '..').
'diff' treats other special files like regular files if they are
specified at the top level, but simply reports their presence when
comparing directories. This means that 'patch' cannot represent changes
to such files. For example, if you change which file a symbolic link
points to, 'diff' outputs the difference between the two files, instead
of the change to the symbolic link.
'diff' should optionally report changes to special files specially,
and 'patch' should be extended to understand these extensions.
Info Catalog
diffutils: Changing Structure
diffutils: Shortcomings
diffutils: Unusual File Names