Programming ZOC (REXX/DDE) → REXX Language Elements

In REXX comments can span multiple lines when they are placed between /* and */. REXX also knows single line comments, which start with a -- sequence and which automatically end when the line ends.

More than one command can be placed in one line by separating them by semicolons.

A command can be continued in the next line by placing an extra comma at the end of the line.
 

Numbers can be used for calculation, counting etc. REXX uses numbers and the arithmetic in a pretty straightforward way:
 

REXX programs often process text in one way or another. While REXX inherently knows no types (values are treated as numbers or strings depending on the context), it is generally better to put all text strings in single or double quotes:
 

You can assign strings to variables. Strings in quotes and string variables can simply be concatenated by writing them after one another, although sometimes the string concatenation operator || can be used for clarity or to resolve ambiguities.:
 

To find errors in your REXX program (or to watch the program execution) you can insert a TRACE A command into your REXX program (usually after the initial comment). With that, the REXX interpreter will display each instruction in the program as it executes it.

TRACE I will show very detailed tracing and TRACE O turns tracing off.

To express conditions in REXX programs, the following conditional operators are used:

Decisions are made using the IF <condition> THEN DO <commands> END ELSE DO <commands> END sequence (see above for conditionals).
A typical program part using an IF command looks like this:
 

The ELSE-part can be omitted if it is not needed. The keywords DO and END can be omitted if only one command is to be executed conditionally.:
 

Loops are expressed in the following form:

DO <count> <commands> END
DO WHILE <condition> <commands> END
DO UNTIL <condition> <commands> END
DO <variable>=<start> TO <end> <commands> END


 
Example:

Loops can be aborted from within using the LEAVE command. The ITERATE command will skip the rest of the loop body for the current iteration and will continue with the next loop iteration.

Jump targets (labels) and subroutines are marked with a name and a colon. To jump to a label, use the SIGNAL command.

The CALL command is used to call a subroutine (which will return to the place it was called from via RETURN).

The following example demonstrates a jump and a call to a subroutine with argument passing:
 

Functions are marked and called like procedures. The difference is that the can return a value to the calling command:
 

It is also possible to call an external script file as a subroutine and pick up a possible result. To do this, the name of the external script files needs to be placed in quotes. The called script then needs to be placed either in the ZOC program folder, in the ZOC Files folder, in the ZOC script files folder or in a folder which is listed in the PATH or REGINA_MACROS variable in the system environment (e.g. C:\1).

Alternately you can specify a full folder and file name for the file. Parameters are passed as usual (separated by commas).

If you have a scriptname or path in a REXX variable the regular call Syntax will not work though, but you can build a string which contains the complete command and pass it through the INTERPRET command (see the sample below).
 

PARSE is a powerful REXX command which can be used to split formatted strings in parts and assign the parts to variables. The syntax is PARSE VALUE <string> WITH <variable>"<delimiter>" …

For example, if you have a string coordinate in the form <index>: <pos-x>/<pos-y> you can easily break it into parts via

PARSE VALUE coord WITH index": "posx"/"posy
 
Example:

ZOC commands are extensions to the REXX language which are implemented as procedures and functions (see ZOC-REXX Commands for a list).

ZOC commands that do not return a value (or if you are not interested in the return value) are called with the procedure call syntax:
CALL <zoc-command> <argument(s)>

ZOC-commands that do return a value are called with the function call syntax:
<result-var>= <zoc-command>(<argument(s)>)

Commands which are intended to be executed by the operating system (like deleting or renaming files), must be addressed to the operating system directly. This can either be done through REXX's ADDRESS CMD command or through ZOC's ZocShell command.
 

The functions below can be used in assignments or in other commands that expect values, e.g. b= ABS(a) or IF ABS(n)>10 THEN ….

 
Note: Only the essential functions and arguments are listed here, for a complete description please see The ZOC REXX Reference (PDF) in your My Documents→ZOC Files→REXX folder.

Please also check the FILEIO sample in SCRIPT\RXSAMPLE\TUTORIAL directory.

It is possible to pass a parameter to a REXX scripts from the ZOC command line (or ZOC user buttons), e.g. ZOC /RUN:script\test.zrx "/RUNARG:Hello, World"

The parameter can be accessed via the ARG(1) function from within the REXX Script and if necessary be split using the PARSE command (it is recommended to subsequently use the STRIP function to remove leading and trailing blanks from the parameters).