|How To Program In ARexx - Part 2 By CROW of The LOC Have you read part 1 of this series, if you have no idea about ARexx I would strongly recommend that you do. In this article I will try to cover how to create, read and write files and also how to create menus. With all file operations the open function/procedure is used, the open has the following structure :- boolean = Open(file, name, [Mode]) file = reference variable for that file. name = is the path and filename. mode = what the user wants to do with the file. Mode values are R = Read (default), W = Write, A = Append. If everything went ok TRUE is returned otherwise FALSE is returned. Creating a file - this example also tells the user if something went wrong. If everything went ok, then you should have a file called tempfile in your RAM: disk with a size of zero bytes. /* Example 11 */ If Open("tempfile", "RAM:Tempfile", "W") Then Call Close("tempfile" Else Say "Unable To Create File, in RAM:" Creating and writing to a file - this time more flexible with constants. NOTE :- to signify a block use Do then End, (BEGIN END for Pascal experts!), if you want more than one statement to be run following a condition then you have to put a Do and an End Around them or you will get an error or weird results. /* Example 12 */ fileptr = "tempfile" path = "RAM:TempFile" If Open(fileptr, path, "W") Then Do /* Here is A DO */ Call Writeln(fileptr, "This is Line 1") Call Writeln(fileptr, "This is Line 2") Call Writeln(fileptr, "This is Line 3") Call Close(fileptr) End /* Here is A END */ Else Say "Unable to create and write file..." Opening a file and reading the contents. /* Example 13 */ fileptr = "tempfile" path = "RAM:TempFile" If Open(fileptr, path, "R") Then Do Do While ~Eof(fileptr) /* While NOT End Of File */ Say Readln(fileptr) /* Read A Line Of Characters */ End Call Close(fileptr) End Else Say "Unable to open and read file..." Creating a menu with validation so invalid options are not processed, also shows how to write procedures. /* Example 14 */ CR = '0A'x /* CR = Carriage Return */ FF = '0C'x /* FF = FormFeed (Clear Screen) */ ClearScreen = FF || CR /* || = concatenate : means Join together */ Do Forever Say ClearScreen Say " (A) - Archive" Say " (B) - Batch" Say " (C) - Catch" Say "" Say " (X) - Exit" Say "" Options Prompt "Enter Choice : "; pull choice 2 Choice = Upper(Chocie) If Choice = "X" Then Do /* This is where we Quit */ Say "Exiting..." Exit End Else If Choice = "A" Then Do Say "Archive" Call WaitForCR() End Else If Choice = "B" Then Do Say "Batch" Call WaitForCR() End Else If Choice = "C" Then Do Say "Catch" Call WaitForCR() End End WaitForCR(): Procedure Say "" Options Prompt "Return to Continue" Do Until C=="" Parse Pull c End Return NOTE : You may have noticed that when you use the function Say, that the cursor goes onto the next line this is not very useful when you have something like (run example 1 if you still do not know what i am wittering about ) :- Say "Enter Your Name : " Parse Pull name So to solve this little quirk, use the following instead :- Options Prompt "Enter Your Name : " Parse Pull name Now all you have to do is then redefine the prompt to what you want it do be after this piece of code. Procedures and Functions. In this part of the article I will try to cover how to create and use procedures and functions. The difference between a function and a procedure, is that a function is something whereas a procedure does something. Please note that this definition does not cover all high level language implementations of functions and procedures.In ARexx procedure and functions seem to merge so that you can write a procedure and function to do the same thing. This is a very simple example of how to define and use a procedure, variables defined in the procedure are only visible to the procedure (there are exceptions, that will be covered later). And variables and constants defined outside of the procedure are normally not visible to a procedure. /* Example 15 */ Call PrettyLine() Exit PrettyLine: Procedure Say "/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\" Return This example shows the most basic example of passing an actual value back with the return statement, this is a function :- /* Example 16 */ Say PI() Exit PI: /* This Is A Function */ Return 3.14159 Now lets show you how to pass values into a procedure, by altering the PrettyLine Procedure in Example 15 so we can specify type of char and number of chars to print :- /* Example 17 */ Say PrintLine("*", 20) /* PrintLine( CharString, NoOfChars ) */ Exit PrintLine: /* This Is A Function */ character = arg(1) /* Get Character To Print */ number = arg(2) /* Get Number Of Chars */ line = "" /* Initialise Line */ Do Number line = line || Character /* Make Line Of What Ever Char Is */ End Return line The above example shows how to pass values to a function, it is quit flexible, as a whole string eg. "Hello" can be passed and not just a single character. The next example takes this slightly further by now adding another parameter so that we now can draw a rectangle instead of just a single line. /* Example 18 */ Say PrintLine("*", 20, 10) /* PrintLine(CharString,NoOfChars,NoLines) */ Exit PrintLine: /* This Is A Function */ CR = "0A"x /* Carriage Return */ character = arg(1) /* Get Character To Print */ number = arg(2) /* Get Number Of Chars */ nolines = arg(3) /* Get Number Of Lines */ line = "" /* Initialise Line */ Do number line = line || Character /* Make Line Of What Ever Char Is */ End box = "" /* Initialise box */ Do nolines box = box || line || CR End Return box The above example (18) uses the || symbol which is the concatenate symbol which is used to join two or more strings together. end.