rhl36.htm

linux的初学电子书

<P>Currently, the enhancements to FlagShip include GUI support. This should further increase the visual appeal of the product.

<BR>

<BR>

<A NAME="E68E315"></A>

<H3 ALIGN=CENTER>

<CENTER>

<FONT SIZE=5 COLOR="#FF0000"><B>dbMAN</B></FONT></CENTER></H3>

<BR>

<P>The dbMAN program is an interpreter. When you start dbMAN, you get a CMD: prompt. This is where you enter all your commands to dbMAN. You can think of this a . prompt in dBASE. For starters, you can type in ASSIST, at the CMD: prompt. ASSIST starts up a 
menu-driven interface similar to ones available with FoxPro or dBASE.

<BR>

<P>The menu-driven interface is not very elaborate. ASSIST only enables one file to be open at a time. This means that it is not possible to set up relations. It is possible to start up a simple program generator from ASSIST. Again, it has a single file 
limitation.

<BR>

<P>You can compile programs in dbMAN. Compiling a program does not produce an executable binary. It produces a .run file, which still requires dbMAN to execute it.

<BR>

<P>It is also possible to enter CREATE REPORT or MODIFY REPORT at the CMD: prompt. This puts you in dbMAN's report writer. The report writer enables display of data by using the relational operators. dbMAN provides a function called PMENU() to create 
pull-down menus. PMENU doesn't have any mechanism for temporarily disabling a menu choice.

<BR>

<P>dbMAN handles windows differently from other XBASE products. Prior to defining a window, you call PUSHWIND() to push the current window onto a stack. When a program is in its initial state, the entire screen is considered to be a window. You then call 
WINDOW() to create the window. When you are finished with it, you call POPWIND(), which removes the window and makes the previous window active.

<BR>

<P>dbMAN enables you to define only one hot key. You do so by invoking the ONKEY() function. This will have no effect until you execute the ON KEY statement. The statement will normally be DO hot-key-handler.

<BR>

<P>The BROWSE command has a long list of options. You can browse only specified fields, and you can specify the width of each field, and whether it is editable. The list of fields can include fields in other files, which is great if you have relationships 
set up.

<BR>

<P>dbMAN does not use either termcap or terminfo. Instead, it includes a file named dbmterm.dbm. This file looks similar to termcap. There are no entries for either xterm or console. You have to create your own entries using the existing entries.

<BR>

<P>dbMAN has no facility for executing functions written in C or assembler. So you have to use what they offer. There were a couple of nasty bugs in the version of dbMAN I evaluated, which was version 5.32. The main one bug I found was that procedure files 
simply didn't work if the procedure file was a .prg. If you compiled the procedure file into a .run file, it worked OK.

<BR>

<P>You can get dbMAN from

<BR>

<UL>

<UL>

<P>VERASOFT Corp.

</UL></UL>

<UL>

<UL>

<P>4340 Alamaden Expressway, #110

</UL></UL>

<UL>

<UL>

<P>San Jose, CA 95118

</UL></UL>

<UL>

<UL>

<P> [phone]

<BR>

</UL></UL>

<BR>

<A NAME="E68E316"></A>

<H3 ALIGN=CENTER>

<CENTER>

<FONT SIZE=5 COLOR="#FF0000"><B>LINCKS</B></FONT></CENTER></H3>

<BR>

<P>LINCKS is an object-oriented database management system. LINCKS is a good system if you intend to use this system on a network and share data via RPC calls. You need to have some experience with networks, as well as an existing network to fully benefit 
from this package. This package is not for a single node system just because it would be an overkill for such a platform.

<BR>

<P>You can get LINCKS from <A HREF="tppmsgs/msgs0.htm#72" tppabs="ftp://sunsite.unc.edu/">sunsite.unc.edu</A> in the /pub/Linux/apps/databases/lincks directory.

<BR>

<P>LINCKS is based on an append-only object-oriented structure. Objects are derived from other objects. Links can be set between objects to define relationships. You define views to an object. A view is used to specify how the data in the object is 
presented to a user. Multiple views can exist for the same object. Views can be inherited.

<BR>

<P>The main interface is xlincks program. Using commands similar to emacs, you can interactively browse through databases. The interface resembles the hypertext functions of a Web page. You click on a highlighted item, and the program leads to a page with 
more information about the topic.

<BR>

<P>Help is available in two forms: context sensitive or as a browsable database. The help file is always a button away&#151;to access help, simply press the Help button. The contents of the help file are well organized and are a good starting place to 
learn ab<A NAME="I2"></A>out LINCKS. The manual is also available in PostScript for the sunsite archives.

<BR>

<P>LINCKS comes with a few programs in its distribution package. You can create new databases using the dbroot command. To prune databases of unreferenced objects, use the cutoff command. The main server for the application is the netserv program which 
fires off a dbs process for each connected client.

<BR>

<BR>

<A NAME="E68E317"></A>

<H3 ALIGN=CENTER>

<CENTER>

<FONT SIZE=5 COLOR="#FF0000"><B>Other Database Products</B></FONT></CENTER></H3>

<BR>

<P>This is a quick overview of some other database management systems for Linux. Most of these are free and can be found on the Internet.

<BR>

<UL>

<UL>

<P>mbase v5.0 is a relational database system originally written for the Amiga and ported to other platforms. It uses a format similar to C to do the database programming. To compile using mbase, you need ncurses and time. My efforts to compile the package 
failed miserably until I made several modifications to the Makefile. If you really want cheap, C-like access to your DBMS, use this package. Otherwise get FlagShip or dbMAN.

<BR>

</UL></UL>

<UL>

<UL>

<P>onyx is a database prototype program based on a format like the C language. The make config command starts the process and a series of questions pop up. Answering all these questions results in configuring Linux.

<BR>

</UL></UL>

<UL>

<UL>

<P>DBF is an XBASE manipulation package and is a collection of utility programs that manipulate dbf files. Some of the utilities, such as dbfadd, add a record or layer of information in the database. dbflist lists the records in the database, dbft lists 
the structure of each database and its items.

<BR>

</UL></UL>

<UL>

<UL>

<P>typhoon is yet another RDBMS. The package is in Beta form. The &quot;most notable&quot; feature for this RDBMS (depending on your point of view) is that it's entirely like C. The problem is that the product still has to mature before being considered a 
viable RDBMS.

<BR>

</UL></UL>

<BR>

<A NAME="E68E318"></A>

<H3 ALIGN=CENTER>

<CENTER>

<FONT SIZE=5 COLOR="#FF0000"><B>Summary</B></FONT></CENTER></H3>

<BR>

<P>This chapter has given you a brief introduction to the various database management systems for Linux. There are many more products for Linux which can provide DBMS solutions. Hopefully, the major manufacturers will soon catch on and provide the database 
solutions for this market.

<P ALIGN=LEFT>

<A HREF="rhl35.htm" tppabs="http://202.113.16.101/%7eeb%7e/Red%20Hat%20Linux%20Unleashed/rhl35.htm" TARGET="_self"><IMG SRC="purprev.gif" tppabs="http://202.113.16.101/%7eeb%7e/Red%20Hat%20Linux%20Unleashed/purprev.gif" WIDTH = 32 HEIGHT = 32 BORDER = 0 ALT="Previous Page"></A>

<A HREF="#I0" TARGET="_self"><IMG SRC="purtop.gif" tppabs="http://202.113.16.101/%7eeb%7e/Red%20Hat%20Linux%20Unleashed/purtop.gif" WIDTH = 32 HEIGHT = 32 BORDER = 0 ALT="Page Top"></A>

<A HREF="index-1.htm" tppabs="http://202.113.16.101/%7eeb%7e/Red%20Hat%20Linux%20Unleashed/index.htm" TARGET="_self"><IMG SRC="purtoc.gif" tppabs="http://202.113.16.101/%7eeb%7e/Red%20Hat%20Linux%20Unleashed/purtoc.gif" WIDTH = 32 HEIGHT = 32 BORDER = 0 ALT="TOC"></A>

<A HREF="rhl37.htm" tppabs="http://202.113.16.101/%7eeb%7e/Red%20Hat%20Linux%20Unleashed/rhl37.htm" TARGET="_self"><IMG SRC="purnext.gif" tppabs="http://202.113.16.101/%7eeb%7e/Red%20Hat%20Linux%20Unleashed/purnext.gif" WIDTH = 32 HEIGHT = 32 BORDER = 0 ALT="Next Page"></A>


</BODY></HTML>