ARexx is aRexxinterpreter forAmiga, written in 1987 by William S. Hawes, with a number of Amiga-specific features beyond standard Rexx. An ARexxscript can communicate with software that implements anARexx port. An Amigaapplication can define a set ofcommands andfunctions for ARexx to address, thus making the capabilities of the software available to an ARexx script.[1] Several applications support running an ARexx script as amacro.
An ARexx script can execute commands and functions in multiple applications which allows a script tointegrate the functionality of the applications. For example, an ARexx script could extract data from adatabase, insert the data into aspreadsheet to perform calculations on the data, then insert tables and charts based on the results into aword processor document.
ARexx allows a script to communicate with applications that are "ARexx compatible" – able to receive commands from ARexx and execute them. Notable examples include: theMicroFiche Filer database application provides extensive ARexx commands, theTextra editor supplied with JForth provides an integrated programming environment, and theAmigaVision multimedia presentation application can control other programs via ARexx.
As in standard Rexx, ARexx usestypeless data representation. Otherprogramming languages distinguish types such asinteger,floating point,string, but Rexx treats all data as text (string). This makes writing code easier, but leads to runtime inefficiency and errors. As is often the case indynamically scoped languages, variables are not declared before using them. They are created on first use.
ARexx provides built-in commands and access to its host Amigalibrary (rexxsyslib.library) as well as other libraries and functions. An Amiga program with an ARexx port canserve its functionality to an ARexx script. An ARexx script can invoke other ARexx scripts.
ARexx was created in 1987, developed for Amiga by William S. Hawes. It is based on the Rexx language described byMike Cowlishaw in the bookThe REXX Language: A Practical Approach to Programming.[2] ARexx was included byCommodore withAmigaOS 2.0 in 1990, and has been included with all subsequent AmigaOS releases. This later version of ARexx follows the official Rexx language closely; Hawes was later involved in drafting theANSI standard for Rexx.
From the ARexx manual:
ARexx was developed on anAmiga 1000 computer with 512k bytes of
memory and two floppy disk drives. The language prototype was
developed inC usingLattice C, and the production version was written
in assembly-language using theMetacomco assembler. The documentation
was created using the TxEd[3] editor, and was set inTeX usingAmigaTeX.
This is a 100% Amiga product.[4]
As ARexx is written in68000assembly language, it cannot function at full speed withPPC CPUs ofMorphOS, a more modern descendant of Amiga. ARexx has not been rewritten for them and is still missing from MorphOS. William Hawes is no longer involved in development of Amiga software and no firm is financing new versions of ARexx. Notwithstanding, the existing version of ARexx continues to be used, although not distributed with MorphOS.
If a user is using a program which builds animations by joining variousbitmap image files but which lacks image processing capabilities, they could write an ARexx script which performs these actions:
EqFiles.rexx[5] is a well-known example of a simple ARexx script written to automate repetitive and boring procedures. This script uses the ALeXcompare program[6] to compare files, and then finds all duplicates in a set of files and returns output by highlighting any results in a different color.
A significant value of ARexx is extending AmigaOS by adding capabilities it lacks. For example, a ARexx program could display a warning message or play an audio alert sound if a certain Amiga program stops, faults or has finished its scheduled job.
The following script is a ARexx script that displays warnings depending on events:
/* Alarm.rexx */ARGeventIFevent=0THENEXITIFevent=1THENSAY"Program has ended unexpectedly"IFevent=2THENSAY"Program has finished its job"IFevent=3THENSAY"Cannot find data in selected directory"
