Third Command: Move About

Unix systems, as with most operating systems including Windows, are based on a hierarchy of directories following from some topmost directory basically represented by an empty slash ‘/’. However, unlike a Window-like environment where you click the directory name to open it and continue your exploration, in a command line environment you have to traverse the directories via command. The command you use is the Unix ‘Change directory’ command, or ‘cd’.

For instance, if you have a directory called cgi-bin located in your current directory, you can change to this directory by using the following:

> host% cd cgi-bin

Typing the ‘ls’ command displays the contents of the cgi-bin directory, if any.

To return to the directory you started from you can use the ‘..’ value, which tells the cd command to move up one directory:

> host% cd..

You can chain your movement requests to move up several directories with one command by using the slash character between the ‘..’ values. The following moves up two levels in the directory hierarchy:

> host% cd ../..

Additionally, you can move down many levels by typing the names of directories you want to traverse, again separated by the slash:

> host% cd shelleyp/forpoets/cgi-bin

Of course, you have to be directly in the directory path of a target directory to be able to use these shortcuts; and you have to know where you’re at relative to the target directory. However, what if you want to access a directory directly without messing with relative locations? Let’s say you’re in the full directory path of ‘home/username/forpoets/cgi-bin’ (assuming your home environment is /home/username) and you want to move to ‘home/username/web/weblog/logs’? The key to directly accessing a directory no matter where you are is to specify the complete directory path, including the beginning slash:

> host% cd /home/shelleyp/forpoets/cgi-bin

Once you’ve discovered the power of directory traversal, you’ll go crazy, winging your way among directories, yours and others, exploring your environment, and generally snooping about. At some point, you’ll get lost and wonder where you are. You’re at X. Now, what is X.