Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15
CONTENTS
Chapter 7. Directory Organization
7.1 What? Me, Organized?
7.2 Many Homes
7.3 Access to Directories
7.4 A bin Directory for Your Programs and Scripts 7.5 Private (Personal) Directories
7.6 Naming Files
7.7 Make More Directories!
7.8 Making Directories Made Easier
7.1 What? Me, Organized?
Computers and offices have one thing in common: you lose things in them. If you walk into my office, you'll see stacks of paper on top of other stacks of paper, with a few magazines and business cards in the mix. I can often find things, but I'd be lying if I said that I could always find that article I was reading the other day!
When you look at a new computer user's home directory (Section 31.11) , you often see something similar to my office. You see a huge number of unrelated files with obscure names. He hasn't created any subdirectories, aside from those the system administrator told him they needed; and those probably aren't even being used. His home directory probably contains programs for several different projects, personal mail, notes from meetings, a few data files, some half-finished documentation, a spreadsheet for
something he started last month but has now forgotten, and so on.
Remember that a computer's filesystem isn't that much different from any other filing system. If you threw all of your papers into one giant filing cabinet without sorting them into different topics and subtopics, the filing cabinet wouldn't do you much good at all: it would just be a mess. On a computer, the solution to this problem is to sort your files into directories, which are analogous to the filing cabinets and drawers.
The Unix filesystem can help you keep all of your material neatly sorted. Your directories are like filing cabinets, with dividers and folders inside them. In this chapter, we'll give some hints for organizing your computer "office." Of course, things occasionally get misplaced even in the most efficient offices. Later we'll show some scripts that use the find (Section 8.3) and grep (Section 9.21) commands to help you find files that are misplaced.
— ML
7.2 Many Homes
Various operating systems store users' home directories in many places, and you've probably already noticed evidence of this throughout this book. Home directories may be in /home/
username
, /u/username
, /Users/username
, or some other, more esoteric location.The simplest way to find out where your system believes your home directory to be is to take advantage of the fact that cd with no arguments changes to your home directory:
% cd
% pwd
/home/users/deb
Generally, the
$HOME
environment variable will point to your home directory:% echo $HOME /home/users/deb
Most shells also expand tilde (
~
) to a user's home directory as well, so ~/archive on my machine becomes /home/users/deb/archive and ~joel/tmp expands to /home/users/joel/tmp.Your home directory is set in your /etc/passwd entry (or equivalent — Netinfo on Darwin and NIS on Solaris store the same information, for example). There is no actual requirement that all users' home directories be in the same directory. In fact, I've seen systems that have lots of users organize home directories by the first few letters of the username (so my home directory there was /home/d/de/deb).
If you add user accounts using a tool rather than by using vipw and adding them by hand, take a peek at the documentation for your tool. It should tell you both where it wants to put home directories by default and how to change that default should you want to.
— DJPH
7.3 Access to Directories
Unix uses the same mode bits (Section 50.2) for directories as for files, but they are interpreted
differently. This interpretation will make sense if you remember that a directory is nothing more than a list of files. Creating a file, renaming a file, or deleting a file from a directory requires changing this list:
therefore, you need write access to the directory to create or delete a file. Modifying a file's contents does not require you to change the directory; therefore, you can modify files even if you don't have write access to the directory (provided that you have write access to the file).
Reading a directory is relatively straightforward: you need read access to list the contents of a directory (find out what files it contains, etc.). If you don't have read access, you can't list the contents of the
directory. However (surprise!), you may still be able to access files in the directory, provided that you already know their names.
Execute access for a directory has no meaning per se, so the designers of Unix have reassigned this. It is called the search bit. Search access is needed to perform any operation within a directory and its
subdirectories. In other words, if you deny execute access to a directory, you are effectively denying access to the directory and everything beneath it in the directory tree. Note that providing search access to
a directory without read access prevents people from listing the directory, but allows them to access files if they know their names. This is particularly useful in situations where you want to allow public access to areas, but only to people who know exactly what files to access; files available via a web server are a good example.
The SUID bit (Section 50.4) is meaningless for directories, but the SGID bit set on a directory affects group ownership of files created in that directory, and the sticky bit prohibits users with write access to the directory from deleting or renaming files that they don't own.
The exception is, of course, that the superuser can do absolutely anything at any time.
— ML
7.4 A bin Directory for Your Programs and Scripts
If you compile programs or write shell scripts, it's good to put them in one directory. This can be a
subdirectory of your home directory. Or, if several people want to use these programs, you could pick any other directory — as long as you have write access to it. Usually, the directory's name is something like bin — though I name mine .bin (with a leading dot) to keep it from cluttering my ls listings.
For instance, to make a bin under your home directory, type: