Everything is a file in a Unix computer, including a device. Devices in the /dev directory differ in that they have major and minor device numbers to tell their drivers how to use them.

File kinds are read from the directory "ls -l" command which reveals "permissions" numerically like 755, 644, 600 representing THREE octal digits "owner", "group" and "others". Each octal digit is the sum of Read = 4, Write = 2, Execute =1. From "ls -l" we see -rwx------ for a 700 file (regular file) .. Expect a "drwxr-xr-x" to be an example of a directory (755). Block and character devices start with b or c, and symbolic links are "l". Example.

Another property pair for files is ownership, "owner" and "group" which usually derive from the users "passwd file" values .. later. Or man passwd.

Common files which we deal directly include text, scripts and HTML files. The command "file filename" offers clues as t file types. Oh yes, xROFF are commonly nroff or troff files comprising the "manual" pages.



gcpacix:~/<1>unix{356} ls -al / | head
total 1110
drwxr-xr-x  18 root  wheel      512 Feb 19  1998 .
drwxr-xr-x  18 root  wheel      512 Feb 19  1998 ..
-rw-r--r--   2 root  wheel      749 Jul 26  1995 .cshrc
-rw-r--r--   2 root  wheel      227 Jun 10  1995 .profile
-rw-rw-r--   1 root  wheel       78 Nov 26  1995 .rhosts
-r--r--r--   1 root  wheel     3425 Jun 10  1995 COPYRIGHT
-rw-rw-r--   1 root  wheel        0 Jun 10  1995 OK
drwxr-xr-x   2 bin   bin        512 May 16  1997 bin
drwxrwxr-x  13 root  wheel     4096 Jun  9  1995 cdrom