2000.11_Out of the Box-Nscache-Cache Browser.pdf

SOFTWARE

OUT OF THE BOX

HIDDEN

TREASURE

CHRIS PERLE

There are thousands of tools and utilities

for Linux. ”Out of the box” takes the pick of

the bunch and each month presents a

program which we consider to be indispens-

able or, perhaps, little known. Here we

examine the cache browser nscache.

After an extensive surfing session using

Netscape , probably the most widely used web

browser under Linux, there is a wealth of files in

your personal disk cache . Netscape itself offers

only very limited capabilities for viewing these files.

NScache , a browser for Netscape’s disk cache,

makes considerably more use of the filed data.

number of other open source projects. As the pro-

gram is only available in compiled form for Red Hat

Linux 6.1, we can obtain the source code and com-

pile it ourselves.

What do we need?

Old acquaintance

To be able to install NScache we need GTK+ (ver-

sion 1.2.0 or later) and the Berkeley Database

Library .

With the file nscache-0.3.tgz on board, we can

move on to the actual installation procedure:

Stefan Ondrejicka, the author of the program, is

already known to many people through pavuk , a

download tool for web pages. NScache has its

homepage at Sourceforge , which is also home to a

tar xzf nscache-0.3.tgz

cd nscache-0.3

./configure

make

su - (enter root-password)

make install

exit

Disk Cache: This is temporary storage space which is created by Netscape on the

hard disk and reduces the need to constantly re-request web pages and images.

This cache is usually located in the directory ~ /.netscape/cache.

~ (Tilde): The tilde is shorthand for the user’s home directory.

GTK+: A library, originally written for the graphics program Gimp, which is used

to program menus, windows and dialog boxes under the X Window system.

If an error occurs at configure or make , this is often

because although the necessary libraries may be

present the corresponding developer packages are

not. Distributions separate these from the actual

libraries. The packages can be identified by the dev

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NScache

OUT OF THE BOX

SOFTWARE

or devel in their name. You need to install these

before you can move on to compiling NScache.

Once the program has been compiled successfully

using make , obtain root rights using the command

” su - ” so that we can install the program below the

/usr/local directory using make install . We relinquish

the root rights again with the exit that follows.

Berkeley Database Library: This library provides functions that can be used to

access files organised in the University of Berkeley’s database format. This format

is widely used under Unix - the library therefore comes as standard in Linux distri-

butions.

X terminal: Programs under the X Window system which provide a text terminal

(similar to a command prompt window under Microsoft Windows.) Widely used X

terminals include xterm, kvt and gnome-terminal.

Shell: One of the most important parts of any Unix system - it provides a com-

mand line-controlled user interface for the system.

Protocol: A standardised procedure which allows programs in a network to com-

municate with one another. Well-known protocols include ftp (”file transfer pro-

tocol”) and http (”hypertext transfer protocol”).

Server: A program that provides a service for use by one or several clients. Exam-

ples of servers include X servers, FTP servers, WWW servers. The term server is also

used to describe the computer on which the program is running.

URL: ”Uniform Resource Locator”, is the unique address of a resource on the Net.

The URL also indicates the transfer protocol, e.g. http://www.linux.de/links/Distri-

butionen/ or ftp://ftp.gwdg.de/linux/mirrors/.

MIME: Multipurpose Internet Mail Extensions, a method of indicating standard-

ised files types. Examples of MIME types include text/plain (plain text file without

formatting) and video/mpeg (mpeg-compressed video stream). MIME is used pri-

marily in mail programs and web browsers.

What is in it?

In order to test NScache open an X terminal and

enter:

nscache &

The ampersand sign ( & ) causes the program speci-

fied before it to run in the background. Without it

the shell in the X terminal would not be able to

process entries again until NScache had finished.

NScache will now output a report, showing a

tree view of the content of the disk cache (Figure 1).

This view comprises three levels:

• Protocol ( ftp or http ),

• Server name and

• File name on the server.

Sections of the tree can be expanded or col-

lapsed at a click of the mouse on the plus or

minus signs. Individual file entries are shown in

the disk cache with their original URL and their

local file name.

It is also possible to display a view which is sort-

ed on the basis of different criteria, as shown in Fig-

ure 2. The view is switched using the two tabs Tree

view and Sorted view . The URL, the size of the file

or the date when it was last accessed can be select-

ed as the criteria by which to sort the view.

specific view programs can be assigned using the

menu item Options/Viewers setup… (Figure 3) using

File viewer. In the example configuration the image

viewing program xv was assigned to the type

image/gif while the X terminal xterm, with a text

browser retrieved in it w3m, was assigned to the

type text/html.

In addition, an external browser (e.g.

netscape , lynx or w3m ) can be given as a URL

viewer . If need be, this retrieves the file concerned

directly from the Net using View URL . In the entry

fields of the configuration dialog %f stands for

the name of the local file and %u for the corre-

sponding URL.

Armed with this handy tool, no-one has any

excuse for trying to tidy up the Netscape disk cache

using the rm -rf ~/.netscape/cache/ sledgehammer

method. Now you can see what’s useful and what

isn’t before you delete it.

Action

If you have selected a file using the left mouse but-

ton, a context menu can be retrieved using the right

mouse button. Probably the most useful actions are

viewing the file using View file and deleting it using

Delete file. We can, therefore, go through the cache

and, if need be, remove particular files. MIME-type

Figure 3: Setting the external viewer

Info

Nscache home page

http://nscache.sourceforge.net

Figure 1: A tree view of the Netscape cache

Figure 2: Sorted view

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