Quick Start Guide

chmod [options] mode files
Changes the access permissions.
The mode parameter has three parts: group, access, and access type. group accepts
the following characters:
u
User
g
Group
o
Others
For access, grant access with + and deny it with -.
The access type is controlled by the following options:
r
Read
w
Write
x
Execute—executing les or changing to the directory
s
Setuid bit—the application or program is started as if it were started by the
owner of the le
As an alternative, a numeric code can be used. The four digits of this code are
composed of the sum of the values 4, 2, and 1—the decimal result of a binary
mask. The rst digit sets the set user ID (SUID) (4), the set group ID (2), and the
sticky (1) bits. The second digit denes the permissions of the owner of the le.
The third digit denes the permissions of the group members and the last digit
sets the permissions for all other users. The read permission is set with 4, the
write permission with 2, and the permission for executing a le is set with 1. The
owner of a le would usually receive a 6 or a 7 for executable les.
gzip [parameters] files
This program compresses the contents of les using complex mathematical algo-
rithms. Files compressed in this way are given the extension .gz and need to be
uncompressed before they can be used. To compress several les or even entire
directories, use the tar command.
-d
Decompresses the packed gzip les so they return to their original size and
can be processed normally (like the command gunzip)
108 Start-Up