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Text File | 1996-03-01 | 10.6 KB | 428 lines

Masterclass Using ARexx with other programs can add new features and automate existing ones. Here's how... We've already seen that ARexx is a powerful and elegant programming language in its own right. However, the real power of ARexx comes when it is combined with other programs. Remember that the Amiga can multitask many applications at once with no effort, and so it's possible to run, say a graphics program, and whilst that is happening start an ARexx script running. It's also possible to make use of specific features of the graphics program from the ARexx script. Here's how. In order for an application program to be used with ARexx, it must have what is referred to as an "ARexx Port". This means that when the operating systems sends a command to a certain location, the application program will recognise it. It's up the the application to deal with the ARexx command, and perform an action or return a value to the ARexx script. For example, an ARexx paint program may accept commands such as "Plot" or "Circle" and perform a suitable action on the screen. Here's an example of how you would use ARexx to work with another program. In this case we'll use AdPro (the Art Department Professional) as our ARexx compatible application program. Remember that an ARexx program or script is simply a plain text file, and so it can be created with any text editor and saved to disk or to RAM disk. Most programs have there own little foibles when it comes to dealing with ARexx, and AdPro is no exception. If you create the script and save it to the directory ADPROSCRIPTS: with a filename such as "f8.adpro", when you press the Funtion8 key AdPro will run the scipt. This is very useful, as it saves you from opening a Shell window and typing "rx myprogram.rexx" everytime -- although occasionally this is exactly what you want to do, especially in long batch processing jobs. Here's what a sample ARexx script looks like, line by line. ARexx works by allowing the host programs to make new functions available, and so some of the commands don't look familiar and certainly won't work with other host programs. This is simply because they are AdPro commands, not ARexx functions. (Note to art people: please include the lines between "%" in a different font, and remove the "%"s. I'm trying to add comments to the listing to explain each line, so please make it clear the text % between markers like this % is not part of the listing, but only explanitory text which should not be typed in.) Example Listing /* Example Program using AdPro */ % All ARexx programs must start with a comment % ADDRESS "ADPro" % This tells the ARexx system which host program to use. This is the special Arexx "Port name" you hear about. If you get it wrong, the script won't work as the AdPro commands won't be found. You must get the upper and lower case letters correct too! % OPTIONS RESULTS % this is a special ARexx command to inform the system that some commands will be returning values to the script for processing % GETFILE % This is an ADPro command, not an ARexx command. It makes AdPro put up a file requestor and ask for a file from the user % filename = ADPRO_RESULT % This is an ARexx command -- the variable called "filename" is set to the value returned in the special variable called ADPRO_RESULT. In this case, ADPRO_RESULT will containt the name of the file the user selected % okay1 "File name is" filename % This is an AdPro command. Rather than use the ARexx SAY to print test to the Shell, this AdPro command opens a window on the AdPro screen and displays the text % lformat "universal" % This is an AdPro command, and it sets the loader to be universal i.e. automatically detect and load the file % load filename % The is an AdPro command, and it loads the file passed to it -- in this case the name was stored in the ARexx variable called "filename" % xsize % This is an AdPro command to get the width of the loaded image file % x=ADPRO_RESULT % This is an ARexx command to assign the width to the variable called "x" % ysize y=ADPRO_RESULT % As before, although this time the height % okay1 "File is " x "wide and " y "tall." % This AdPro command will print text in a box on the AdPro screen % ------------------------------------------------- You can see there is really nothing to it, because AdPro does all the hard work for us. All we do is automate the pressing of the buttons by calling the relevant commands directly. The AdPro documentation includes full details of all the commands which are available, and many example script are supplied. Some of the scripts will process all the frames in an animation, or animate ripple effects. Anything which AdPro can do can be automated, which is an excellent way to save time. This is what "Batch processing" is all about. You set up the computer to repeat a task, and then you go on and do something else (such as going to bed) whilst it gets on with it. You are perform tedious operations such as loading in a thousand images in JPEG format, scaling them and re-saving them in GIF format. You can also use batch processing in a creative way: For example, you might want to make an animation in which the screen fades out and fades in -- an AdPro script can load each frame in turn, adust the colours and re-save it. Or you might want to add ripple effects as though the image was underwater and rain drops were falling on it. Once again, an ARexx script can handle all this for you. Sadly AdPro is rather hard to get hold of these days, so hopefully the next release of Photogenics will feature an ARexx port. Don't think that graphics programs are the only applications which benefit from ARexx. Final Writer is an superb Amiga "Page Processor" program, and the authors were smart enough to include a full ARexx port. As a result, hundreds of ARexx macros have been written and many are available for free from the Aminet (either the CDROMS or the Internet site). You'll find scripts which will write business letters for you, draw graphics, wrap text in circles and automatically create drop shadow effects. Advanced ARexx users can take advantage of the many libraries and routines available. For example, it's possible to create a graphical front end with gadgets, windows and requestors all from an ARexx script. We'll take a look at these next time. Box out: Speeding up Arexx programs ----------------------------------- ARexx is an interpreted language, which means it is always going to run rather slowly. One way to speed up ARexx programs is to compile them, and there are one or two programs which will do this available. However, it's simpler to simply stream-line the existing script as much as Possible: and that is exactly what the program "RexxOpt" I found on Aminet does. Take a look at the following extracts from an ARexx script, showing before and after. Although this is clearly not good programming practice, it is a fair way to get a little extra speed from programs you have already written and tested. Make sure you keep a copy of the original though! BEFORE ------ (note: please use a small tight font for the listings, it's not for typing in rather for demonstrating how the compression works!) /* Search for file names ending in #?bak, and then delete them if necessary. © John Kennedy */ address command /* Use AmigaDOS */ /* First, generate list of files & sizes */ Say "Making list of all files in current directory...." 'list lformat "%p%n %l" all files > t:templist' /* Now, search for those ending in .bak */ Say "Adding up file sizes.." infile='infile' outfile='outfile' total_size=0 number=0 call open(outfile,'t:report','w') call open(infile,"t:templist",'r') do while ~eof(infile) data=readln(infile) if data~='' then do parse var data namepath " " size if size='empty' then size=0 test=right(namepath,4) if (test='.bak') then do total_size=total_size+size number=number+1 call writeln(outfile,namepath) end end end call close(infile) call close(outfile) AFTER ----- /* Optimized with RexxOpt 1.7 */ address command;Say "Making list of all files in current directory....";'list lformat "%p%n %l" all files > t:templist';Say "Adding up file sizes..";infile='infile';outfile='outfile';total_size=0;numb er=0;call open(outfile,'t:report','w');call open(infile,"t:templist",'r');do while ~eof(infile);data=readln(infile);if data~='' then;do;parse var data namepath " " size;if size='empty' then size=0;test=right(namepath,4);if (test='.bak') then;do;total_size=total_size+size;number=number+1;call writeln(outfile,namepath);end;end;end;call close(infile);call close(outfile) Box out: ARexx compatible programs ----------------------------------- Here is a list, by no means comprehensive, of some of the more popular programs to feature ARexx ports. If an applicate program has an ARexx Port, you can write an ARexx script to call various features of the application, or create macros for use within the program. For example, as both the V-Lab video digitiser and AdPro image processor have Arexx ports, you could write a script to grab frames from video, scale them, re-colour them, and save them to disk: all automatically. Ami-Back Disk backup and maintainance suite. AMosaic World Wide Web browser. AmiTCP/IP TCP/IP networking suite. AMOS Professional Programming language. Art Department Professional Image processor. Bars & Pipes Professional MIDI sequencer and multimedia authoring tool. Blitz Basic II Programming language. CanDo Programming language and multimedia authoring tool. CygnusEd Professional Text editor DeliTracker MOD player Directory Opus File management. DirWorks File management. Distant Suns Astronomy program. Final Copy Page publisher. GPFax Use modem as fax machine. ImageFX Image processor. LightWave Image renderer. MainActor Animation player. Maple Mathematics engine. Music-X 2 MIDI sequencer. NComm Terminal emulator. Quarterback Disk backup and maintainance suite. Real3D Image renderer. SnoopDOS System monitor. Spot FidoNet mail manager. Termite Terminal emulator. Thor Mail/news manager. TrapDoor FidoNet mailer. TypeSmith Font editor. VistaPro Landscape generator. V-Lab Video digitiser. Xi-Paint Paint package. captions -------- may1.iff FinalWriter is an excellent Page Publishing program, and it features an ARexx port. This means that it is possible add your own functions such as the bar chart utility. may2.iff Art Department Professional is (or at least was) the premier image processing program. It's ARexx facilities made it the ideal batch processing utility.