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Getting Around In The UNIX Directory Structure

NOTE: This Tip Sheet assumes that the reader has a copy of a telnet application like EWAN or NCSA Telnet, and is familiar with its use. If you do not have a telnet application, you can get one several ways. If you are a SkyPoint Macintosh user you can download the standard SkyPoint software package, which includes NCSA Telnet. Windows 95 users have a telnet window already installed. Otherwise, all platform users can access on the Web, do a search for telnet applications, and download one for free.

Where Am I? - pwd

Usage: pwd
At a prompt, type in pwd and hit return. This will always print the full pathname of the directory you are in. This is very userful when you are far away from your home directory and have lost track of where you are.

What Is In This Directory? - ls

Usage: ls [option] {names}
  -a = List all files including those that are normally hidden with a . before them
  -F = Show file types by adding / to directories, * to executables, @ to symbolic links
  -l = Long format listing for detailed information on permissions, owner, size, symbolic link, type, and modification time
  -t = List files by modification time (newest first)

Example: ls -l

total 14          
drwxrwxrwx 2 aquila skyshell 512 Jul 8 1996 Mail/
-rwxrwxrwx 1 aquila skyshell 0 Jan 16 09:46 config.sys*
lrwxrwxrwx 1 aquila skyshell 35 Feb 6 13:09 ftp -> /var/spool/ftp/pub/members/a/aquila/
-rw-r--r-- 1 aquila skyshell 1756 Apr 2 13:13 rhostinfo

You are probably already familiar with the similar DOS command, dir. The options shown are not the only ones by any means, but they are the most useful ones for beginning UNIX users.

Let's look at the above example and see what it means. The field at the far left is the permissions field. If you want more information on permissions, please see SkyPoint User Tips on Unix Permissions. The second field is the owner's logon name, in this case "aquila." The third field, showing "skyshell," is the group the owner belongs to. The fourth field is the file size in kbytes. Field five is the creation/modification date. If the field shows a date and time but no year, as in the "rhostinfo" file, that means that the file was created this year. The rightmost field is the file or directory name. Please notice that the name "Mail" is followed by a "/". This means that this is another directory. Another way to tell if something is a directory is to see if the leftmost character in the permissions field is a "d". The "*" at the end of "config.sys" means that this is an executable file. When you see the "->" arrow in a name followed by a directory path, as in the "ftp" name, that means that the name before the arrow is actually a symbolic link pointing to another file or directory. The path after the arrow is the actual file or directory being pointed to. Also, if the first character in the permissions field is an "l", that means that the name is a link.

The best way to learn how to use these commands is by trying them out and seeing what they do. Let's look at one more example of how ls can be used. What if the directory we wanted to list had dozens of files in it, and we just wanted to find out if one starting with an "ma" was there? Rather than listing all those files and looking through them, all the user would have to do is type ls -l ma* and hit the return key. That would list all the files, links, and subdirectories in that directory starting with the letters "ma," and give us the long form of the information. Of course, if the user only wanted to see the files without getting the additional information, she would just type ls ma* and hit return.

I Want To Go Somewhere Else - cd

Usage: cd [directory path]

DOS users are familiar with the cd command already. However, they should note that, unlike the DOS backward- slash (\), UNIX uses a forward-slash (/) in showing its directory structure. For example, a user might want to find a file in another member's (aquila's) ftp site, /var/spool/ftp/pub/members/a/aquila. She would type cd /var/spool/ftp/pub/members/a/aquila and hit the return key.

One other useful trick with the cd command is that if you ever get lost or just want to get back to your home directory from anywhere in the system, type cd and hit the return key. You will immediately be put back to your home directory.


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