The Unix operating system is a little bit like that. One of its real
advantages is a filesystem that lets you organize your personal files
into a hierarchical directory tree just like the much bigger tree
that encompasses the entire filesystem. You can squirrel away all
kinds of useful information into neat pigeonholes.
While your personal directory hierarchy is usually only two or three
levels deep, for all practical purposes it can have as many levels as
you like. And, as is true of any powerful and flexible tool, problems
lie in wait for the sorcerer's apprentice.
Directories and files grow increasingly complex the longer you use
the system, with more forgotten files and more detailed organization.
This chapter will tackle the problems that can arise when you want to
move a block of files (in one or many directories) from one place to
another.