09-08-2012, 03:32 PM
Fundamental UNIX Commands
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INTRODUCTION
The most distinguishing characteristic of the UNIX operating system is the file
system structure. The file system structure resembles an inverted tree, with the
user's files as leaves along the bottom and the root at the top. The user's home
directory (the directory you are placed in when you log in) is placed at a specific
point in the structure but the user is not limited to that directory. It is possible to
move around in the tree - up, down, and sideways - into directories belonging to
other users and/or the system. Users can protect their files and directories from the
prying eyes of others by changing access permissions.
Each file and directory has a path name which uniquely identifies it. The path is
described, starting with the root, down through the branches of the tree, to the
directory containing the file. Filenames must be unique within a directory. On
Central UNIX, this tree structure is spread over all of the sites that exist in the
cluster
CHANGING FILE ACCESS PERMISSIONS
Access permissions fall into two categories, base permissions that exist on most
UNIX systems, and extended permissions, available on most POSIX based systems
such as AIX. This section addresses those forms for setting permissions.
NOTE: Systems using AFS (Andrew File System) and DFS (Distributed File
System) DO NOT use base permissions except for the user level only, group
and other permissions must be set through extended permissions.
EXTENDED PERMISSIONS (AIX FILESYSTEMS ONLY)
Extended permissions are set via Access Control Lists and the three commands
that manipulate them. Extended permissions allow access to be controlled to
the user or group level within the UNIX accounting structure. These
commands are "aclget ", "aclput ", and "acledit " and are described below. A
fourth command developed at Cal Poly " aclmod " is also described.
TO THE TERMINAL PRINTER
The user may print files to the printer by use of either the cat command or the
pr command. Please refer to the documentation for your terminal or terminal
emulation software for more information on enabling a local printer. When the
printer is enabled, the cat command will copy the specified file to the terminal
and the printer. The pr command does the same as cat but adds page headers.
In either case (cat or pr), the terminal printer should be correctly enabled
immediately before the user types the <CR> on the command line. The printer
should be released when the file has finished printing.